Indeed very strange problem, but it shouldn't have anything to do with the spoiler itself (simple code)
I remembered that someone else reported something similar before, and there are complaints from some users that they can't see the spoiler content, no matter the likes. It still happens. Now I'm wondering if it's something to do with platforms and protocols.
P.S.
I "spoilerised" the picture in the post he mentioned, but I didn't touch the rest. And for that I use a button in the editor, just again - no relation to the problem (simple code), I can also type it by hand.
@JmaCWQ
I recommended two browsers, you should have tried them (to compare the situation with the known facts)
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