You might like to check that the mast is vertical to the beam of the yacht. This is impossible to do accurately while the yacht is afloat but it is possible to get a close idea using a couple of levels if you are anchored in "mill pond" conditions.

Are your side stays equally tensioned and is your mast straight??

Another thing to check is your trim, ballast and weight distribution in the yacht.

I believe generally speaking, all yachts sail slightly better on one tack than the other but it is not usually noticeable.

I am assuming your sheeting blocks are in the same position either side. Cheers

Vertical mast can be fairly easily checked with the use of halyards. Fix them to just touch the gunwale at a certain point and then check that they match length on the opposite side.

Ensure that spreader angles and lengths are the same.

Sometimes it's the result of foils not being symmetrical. A home-built rudder on a yacht that I sailed on last season always performed poorly on one board. A close look at the rudder showed that its profile was different on the port from starboard sides.

Good luck and most often it would be the issue of maast not being vertical.