Thanks for reaching out. We are sorry for the trouble. We are here to help.
Could you please share the exact version of Lightroom you are working on & the specific operating system you are working on? Lightroom 5.4 was released for Windows & macOS & Lightroom mobile 7.4 for (iOS/Android).
If you are working on a mobile device, is it an Android or iOS-based device (iPhone/iPad)? How much free space does your mobile have?
Does this happen when working on specific files or file types (JPEG or RAW)?
If you are working on Adobe Lightroom (cloud) on a desktop (Windows/macOS), please go to Lightroom > Preferences > Performance > Use Graphics Processor > Set it to Off if it is on Custom or Auto.
Please share more details about the issue so that we can suggest better.
We hope to hear from you soon,