Comment 1 for bug 1620341

There's not a lot to go on here, unfortunately. The problem of image cache manager deleting things that are still in use is well known, and in fact we have workarounds elsewhere in the code for it. Out of interest I'd be curious to know how this impacts users, because it also means that the workaround code is broken and/or incomplete.

The underlying problem is obviously image cache manager itself. Without anything more specific to go on I can throw up a patch which fixes a couple of races I was vaguely aware of but hadn't gotten round to addressing. I can't guarantee it will fix your problem, but it might.