You can process raw data in Single mode, so there will be no need to use a log from the base. You can change the mode in RTKPost Options/Settings1/Positioning mode.
Could you please share photos of the whole setup on a plane?
And if it’s possible, post photos of the area where you accomplished your tests.
I also agree with @tobias-dahms’s suggestion, please test it as well. We need to understand what influence the signal reception quality.