So, I wonder why has this become an issue all of a sudden?
From going through the exercise of changing an SM, I do know that timing can be critical.
While it will depend on the OC’s contract with the SM, there is usually a requirement to give enough notice of the OC’s termination decision before the anniversary of the SM’s contract. Else the SM’s contract is automatically renewed.
And with R allowed to vote, there is the potential that the vote will be 2-2. In which case the chair gets a casting vote. With the chair in favor of the SM, we know which way that casting vote will go…
If it really is likely to be a numbers game, perhaps the OP is best to call a Special General Meeting. At least that will resolve the matter.