Is it totally implausible that agents of a Central Bank could be quietly buying BTC and systematically dumping at a loss at precise times in order to suppress price?
Net losses would be negligible for that type of entity and might easily be swept under the rug in a context of monetary expansion.
This is delusional thinking. BTC does not register enough for them to take all these trouble. In future maybe, but certainly not now.
The market capitalization of BTC is too small to bother.