I've been battling this occasional problem of machines being hard to pull backwards or no traction since new .I have 2015 vintage mower ( pretty sure they are ). All 4 have the same model numbers .But 2 of them have slight differences
Notice the shine mark on the belt guide . This ones to high and when engaged will hit cover preventing it from engaging all the way plus will also make them hard to pull back .
Did adjusts them originally as per the operator hand book we have here . Down a little further made the troubled ones work as they should .
Notice the step jack
Must have been changed mid season .
Same for the belt drives
A bit different .
One of the Guys on Twitter mention that this is one good reason to give your serial # too when ordering parts .