Four main causes were suggested as the cause of the problem:
1) Malicious actors (miners or node relayers operating DDOS)
2) Geographical isolation issues
3) Incompatible versions of network node and wallet software
4) Miners rejecting transactions mistakenly
Funkenstein, you are very mistaken, the only correct answer is answer 3). I wrote you this on Discord.
All unconfirmed transactions are made by the windows wallet of the old version, and the pools work with the new version of the wallet. They are not compatible for transactions, they can only confirm transactions of their versions, otherwise they are compatible. That is - the windows wallet transactions will be confirmed only by the blocks found under the old version of the wallet, and vice versa. Blocks without transactions confirm both wallets.
You have only one way out - this is updating your windows wallet or rolling back pools to the old version. A very big mistake was to leave on git. two versions of the wallet.