Before I comment, I want to preface this by saying I'm not 'defending' this game nor am I insisting it's perfect in every single way. My explanations are my own dumb thoughts and I could be right and I could be wrong. I'm just going to explain things as I see them in an effort to maybe get to the bottom of your clips.
@BoredJason13 wrote:Why in the first clip does the D player that comes onto the ice, beeline straight to the net instead of staying up on the line? I understand the center coming up to the line, but as soon as the defender turns shouldn’t the center go the line of what the AI does with the D??
I think you're right; the logic here appears to be that there's already 3 high with one of the 3 being the centre who has possession:

This reason, combined with the fact that the puck carrying centre is actually beelining right for the LD's position - leads me to think the logic is that the LD has an open lane to the abandoned net-front (which would normally be occupied by the Centre)


This may have to do with your current defensive pairing strategy, this could be by design and intended behaviour under normal circumstances, or a combination of the two.

On a scale of 1-10, this provides many variances in how that scenario would play out.
Based on your clip, I'd guess Hold Line / Pinch is closer to 10 than it is to 0, which would mean they're encouraged to jump up. You'll need to play with this setting to get it to a spot that fits your play style.
@BoredJason13 wrote:Second clip in tweet, on FULL PRESSURE, why on a loose puck does the player CLOSEST to the puck skate away?? And in turn it took me three tries of changing players to get to this D player. The defenseman can clearly get to the puck before anyone but why is he going back on defense at full pressure?? Please make it make sense
It doesn't make sense at all. Looks like a flaw in the positioning logic when the puck is knocked loose. I wouldn't be surprised if this is somehow by design and you've exposed a critical flaw in the atrocious pressure system. Definitely a problem that should be looked at.