Anyone know how to fix this? Getting this error on multiple photos from a collection, but not all.

My two suggested troubleshooting steps are more about narrowing down the cause, in case it happens again to you and to help others. If you can upload directly from the browser, that indicates the issue is somewhere in LR and not with the photos themselves. If you can publish an imported copy of the photo, that indicates the problem is with the metadata stored in the catalog.

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I was going to try the browser upload and that is when I discovered that the photos were already there. Have not tried making a copy, but since they are already uploaded not sure if that would be a helpful thing to try.

Strange indeed. The Friedl plugin is more likely to report accurately errors returned by Flickr. Some more things you might try:

1. Try uploading the photos directly from a Web browser to Flickr.

2. Import a copy of one or more of the photos into your LR and see if you can publish them. 

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This error (and very similar ones) have been reported occasionally over the years by users publishing to Flickr:

https://feedback.photoshop.com/photoshop_family/topics/lightroom_5_error_uploading_to_flickr_facebook

https://feedback.photoshop.com/photoshop_family/topics/publish-to-flicker-using-publishing-services-error

Flickr has never been particularly reliable ("Flakr"), though since being purchased by Smugmug it appears to have started climbing out of the deep hole dug by Yahoo's death spiral. Combine that with a built-in LR Flickr plugin that Adobe only half-heartedly supports, and the result is mysterious error messages year after year.

Many people find this third-party Flickr plugin much more reliable, with error messages that are more helpful: 

http://regex.info/blog/lightroom-goodies/flickr

The author has an excellent reputation for maintaining his plugins (he helped design the original LR publishing architecture).

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What precisely are you doing in LR when that happens?  (Which commands, what photos are selected)

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