I play an Oathbreaker Paladin and I have never had this problem. Usually, I’m the one shoving things to their death if I absolutely must.
So, your positioning needs reconsidering, or you need to use your tank/STR character to force an opening so you can relocate. OR you’re just really unlucky.
From my perspective, if you’re falling to your death that much, it’s more likely you either like standing on cliffs or you’re trying to make excessive use of High Ground attack bonus, which IMO isn’t enough to justify me wasting a move turn repositioning and setting myself up for a potential fall.
By all accounts, this is not a bug, nor is it a problem if you adapt your strategy to prevent such a thing.