Normally when one partner is acting like this they want out, can they be bought out?
If you have introduced external money recently and you are trying to even that out with them contributing or adjusting shares it could be a likely time to split.
Much easier with well written share holders agreements but it happens all the time… some times sensibly, sometime not.
Is the business partner adding any value to the business?
Happy to chat about what options you may have to secure funding to buy out.