disclaimer: the tumblr servers are fickle when it comes to upload errors. there are no fail-safe ways to fix or prevent them, except for not uploading a gif in the first place. these are purely my own experiences with the error that will hopefully save you some frustration and effort.
upload errors tend to happen when gifs are:
preventing an error is not always in your control. sometimes the servers glitch because for some unlogical reason, they have a problem with the caps. it is not unusual for caps from the same video to get the same error.
there are basically three types of errors:
1. moderately annoying glitch:
your gif is too bright. this usually happens with gifs that are, well, really bright and saturated. the best way to handle this glitch is to adjust your colouring to something less explosive. brightness/contrast and hue/saturation (or, preferably vibrance) adjustment layers are helpful in bringing the tones of your gif to a more tumblr pleasing level. you can check whether you’re dealing with this gif by trying to upload the gif without colouring. if this works, a less bright colouring should work too.
for example, this colouring causes an error:
but this slightly less bright gif works fine:
2. incredibly bothersome glitch:
sometimes, for whatever crazy reason, you’ll even get an error when you try uploading a gif without any adjustments or meddling with the colours whatsoever. in this case, the first thing you should try is greyscaling the gif. either use a b/w adjustment layer or a gradient map to make the colouring monochrome. if tumblr accepts this colouring, you should be able to edit the colouring and even add colours (for example, a gradient set to lighten).
for example, this (frankly not very bright) colouring causes error:
just like the unedited version:
but, *drumroll*, a monochrome colouring magically works!
(I could go on forever, seeing as I have beyond 26 versions of this gif)
3. the lost cause
there is no logic, there are no rules, it just randomly happens and there is nothing you can do about it. some gifs just don’t work, even in a monochrome colouring. all you can do is try not to destroy too many windows and hope that some kind of sorcery happens and the servers change their mind about not accepting the gif. it is extremely rare, but it does happen.
an example of this pile of frustration is this gif:
it. just. does. not. want. to. work.
as I said before, these are merely my experiences and ways not to destroy everything in reaching distance. if you have different experiences or ways to handle the error, I’d like to hear about it!