Lightroom freezes when toggling “before/after” view with Subject Mask active

[Kirrrrrri]

When working with multiple masks in Lightroom, the app consistently freezes when toggling the “before/after” view (using either the “Eye” icon or the “\” keyboard shortcut) while the top mask is a Subject Mask.

Steps to reproduce:

1. Create two masks on an image.
2. Make the top mask a Subject Mask.
3. Apply any mask adjustments.
4. Repeatedly toggle the “Eye” icon or press “\” multiple times to view before/after.
5. Lightroom will eventually freeze and become unresponsive.

System info:

macOS Sequoia (reproduced on multiple devices)

Lightroom Classic 14.5.1

Screen recording demonstrating the issue is attached.

Note: In the video, I’m clicking pretty fast just to trigger the freeze reliably, but in normal use Lightroom can still hang after just a few before/after checks.

[Aleke]

Hi @Kirrrrrri, welcome to the community!
I tried testing on my end but wasn’t able to reproduce the issue. One thing that might help is resetting your Lightroom Classic preferences, as that can often clear up odd glitches. Here’s how you can do that: https://adobe.ly/43d09GK

If that doesn’t do the trick, could you share your System Info with us? You’ll find it in Lightroom Classic under Help > System Info. Just copy it into a text file and attach it to your reply, or feel free to share it through Google Drive, WeTransfer, or any other file-sharing service you prefer.
Thanks so much, and we’ll do our best to help get this sorted!
Alek

[Kirrrrrri]

Hi @Aleke! Thanks for the quick reply. I’ve attached my system info to this message.

I’ve already tried resetting Lightroom by removing preferences, but that didn’t resolve the issue.

I also tested it on several devices, including one with a fresh Lightroom installation (Lightroom was never installed on it before), and got the same result.

The issue is consistent in Lightroom Classic 14.5.1. In version 14.3.1 it’s less severe - the app occasionally freezes but unfreezes after a few seconds, whereas in the latest version, it stays frozen indefinitely.

[Sameer K]

Hey, @defaulta7rtyzl08ukc. Thanks for the details. We're unable to reproduce this with a few masks. Could share the number of masks, maybe share a sample full-size DNG with masks and a video of what you see. 

Thanks!
Sameer K
(Type '@' and type my name to mention me when you reply)

[Kirrrrrri]

Hi @Sameer K!

It happens with any image.

I’m attaching a new screen recording where I demonstrate the following steps:

1. I completely reset Lightroom Classic by removing these files:

• Catalog folder.
• Lightroom folder from Application Support.
• Lightroom Preferences.

2. I download a random image from Unsplash that works with the Subject Mask.

3. I import this image into Lightroom and switch to the Develop module.

4. I apply one Brush mask.

5. I apply a second Subject Mask and adjust a few sliders (the masks overlap — maybe that’s relevant).

6. I click the Eye icon on the top mask to toggle before/after.

7. I also press the \ key to toggle before/after.

Result: Lightroom freezes. In the video, it takes about 30 seconds of rapid clicking on the mask (so it’s more of a stress test showcased), but as mentioned earlier, in normal use it can randomly freeze after just a few clicks on the Eye icon. The more images I’ve worked on in one session, the higher the chance that Lightroom will freeze after just a couple of before/after toggles.

Tested this on a MacBook Pro M4 (16GB RAM), Mac Mini M4 (24GB RAM), and Mac Mini M2 Pro (16 GB RAM).

[Sameer K]

Thanks for sharing the video, @defaulta7rtyzl08ukc. When you use the \ key for before/after view, you view the image as a whole, but when you use the Eye button on a mask, just the mask is viewed. 

On the other hand, the mask toggle adds to the history panel, so when you repeatedly click on it, the history states are populated. 

Please check if "Automatically write to XMP" is enabled in Lightroom Classic > Catalog Settings > File handling. 

Let me know how it goes. Thanks!
Sameer K
(Type '@' and type my name to mention me when you reply)

[Kirrrrrri]

Hi!

Most freezes seem to occur after clicking the Eye button on a mask, as shown in the video.

It looks like the issue might be related to the history states. I’d really appreciate it if your tech team could take a look. As I mentioned before, in version 14.3.1 freezes occurred as well, but the program would unfreeze after a few seconds. In the latest version, however, it just gets stuck and I have to Force Quit.

“Automatically write to XMP” is disabled in my catalog settings.

Thanks!

[Kirrrrrri]

@Sameer K Hello again!

I’m attaching a screen recording from the recent Lightroom Classic 15.0 release.

This time, the freeze happened just a few clicks after using the Eye icon - right after launching Lightroom on a newly imported image.

One interesting thing I noticed is that the freeze almost always occurs after the “Rename Mask” window appears. Once that window pops up, it’s usually a sign that Lightroom will freeze within the next few clicks on the Eye button.

[Kirrrrrri]

@Sameer K So yeah, if it’s hard to reproduce on your end, try opening the “Rename Mask” window first, click Cancel, and then click the Eye icon a few times. Lightroom should freeze pretty consistently after that.

[Anshul_Saini]

Hi @Kirrrrrri,

Thanks for the additional recordings and details. We attempted to reproduce the behavior again on our test systems, including the Rename Mask workflow you described, but we’re still unable to trigger the freeze on our side.

To help us narrow this down further, please update to the latest version of Lightroom Classic (v15.0.1) and check if the issue still occurs. If it does, please share the following so we can test with the same conditions:

• Your full System Info from the Help menu in Lightroom Classic (copy and paste it into your reply).
• A sample DNG or RAW file along with its XMP file that includes the masks you demonstrated.
• If possible, confirm the exact steps you followed on that file after importing it into v15.0.1.

Once we have the same file and mask structure, we can attempt to reproduce the issue exactly as shown in your screen recording.

Thanks again for your patience and for helping us investigate this.

Best,

Anshul Saini