Inconsistent club responses

What's also strange is that the player accepted a contract offer negotiation, then rejected the contract, and now I'm required to renegotiate with the club, and now they suddenly won't accept the transfer offer either...

This logic is working as intended. The financial gain of possibly selling the goalkeeper will mean the club will be more interested in a transfer rather than a loan even if it leaves them short.

Hm, then how come they reject the offer of a swap deal with me sending a younger keeper of similar ability the other way? And why did they refuse my offer after 1) accepting it before the player reneged on the tentatively agreed upon contract and 2) saying I could resubmit the same offer? It's all very difficult to understand due to the lack of clarity / explanation in seemingly random responses.