This image proxy server has caused at least 23 mystery caches of mine getting unexpected outcomes since this week. As the result, all those puzzles have become unsolvable.
I contacted HQ and the only suggestion I received is "using 'Add image' in Edit page to upload all images to geocaching gallery". Thanks a lot! Why hadn't I thought of such wonderful idea earlier!
I believe it's no point to contact HQ again. I'm now working on my puzzles to make them solvable again.