I suppose you had no luck there.

I believe your suggestion is mostly right: after 6 hours, all wallets consider themselves out-of-sync, at least when restarted. I also made a similar hack to try to move things around but unfortunately this time none of my current coin chunks meet the necessary criteria to stake: being still for 1 hour is not enough, although in practice it usually is. There is a flag called "stake-modifier". Your chunks can only stake if there is a block with this flag at least an hour in the future since your chunk was last moved/staked. And this is exactly my problem: most of my chunks are within an hour of that last block, so not eligible at all. I have 2 other chunks that are older than the current last block, just over an hour, but unfortunately the last 2 blocks in the chain (those over an hour for me) do not have the necessary "stake-modifier" flag so I cannot make them stake.
The solution seems to be someone with eligible chunks to try to stake hacking the wallet code and bypassing that 6-hour sync limit. If that is not feasible, I could try to solve it if someone provides me with a private key to an address with some eligible chunks (any amount should do the trick, even 1 CBX). Of course I wouldn't touch that address and then whoever owned it could move it away after the chain is fixed. Trying to move funds won't help as it won't be moved for the time being and it would also reset the 1-hour resting period, making things worse.