Hi Edh
The only thing I can think is too much Alcohol has evaporated from the copal and rather it being a thick syrup it has become too dense to merge with the oils. The oils and the Turpentine or turps substitute should mix with no trouble. I should try removing the glob of what I think is Copal put in another container and add some Alcohol to make it of a thinner consistency and try to mix it in with the Oils again. The turpentine is there to slow the oil drying as you rub it on the wood so adding more will just prolongs the rubbing time.
I must admit I have not had a problem like yours and as you can see from the photographs all the oil constituents mixed without a problem.
Ernie
