It's all good Jorge. I'm just trying to get you enough input to replicate and fix.

If you want, I can check it for you in my setup when you're ready for that.

Just remember the middle edges between the monitors; The are both there and not there.

Ie. Primary Left; Secondary Right

Cross over edges between them; right side of left monitor and left side of right monitor.

When a dock is set to either of those edges and also set to collapse: hitting the thin pixel line "hot spot" that either of those edges represent is not easy.

The tendancy is to mouse right through the un-collapse trigger of the "edge".

The faster the uncollapse activation is set the easier it get's to have it pop open. The slower the activation is set the harder it is. BUT, setting activation timing is universal to all the WS components

The use of the middle edges between the monitors is very handy but has operational issues with activation when collapsed.

Yes, as you've found out, you shouldn't use the edges common to both monitors to harbour auto-hide docks, since there is effectively 'nothing' to bump there.