>> It seems to me that the simplest approach to dealing with this Gordian knot is to use Alexander's approach and, rather than spend
>> untold effort trying to untangle it, ...
Well, this is getting nowhere, isn't it? Mind set, perhaps. It's not a horrendous technical conundrum. I don't want to fix Opera or find why the problem is happening. At this point, all I'm asking is when it happens and when it doesn't.
This requires no effort. I use the computer as usual, note when the problem comes and when it goes. Doing that (and about three minutes' extra work doing things to narrow it down like changing the cache size, and changing when I run CCleaner and wipe the LOS's and all), I have a good idea of what triggers the problem. Not the ultimate cause, just the proximate one (the circumstances).
I pretty much know when the problem happens now, and I can turn it off at will. I'd rather narrow it down more (remember, the goal is to be able to turn the problem on, not off), but that will come, and I'm in no hurry. Then I can immediately and conclusively confirm any proposed fix. All pretty much effortless. That confirmation step is the important difference between a problem that's solved and one that's known to be solved.