Illustrator V29 brush behaving oddly

What am I missing here? I have Illustrator v28.7.2 and Illustrator v29.0 on my computer and I can't figure out why the brush tool is behaving completely different from one version to the next. 

In this video the v28.7.2 brush behaves the same as it has for years in illustrator. In this v29.0 example it isn't really working at all; deleteing previously drawn lines and averaging the art into something unrecognizable. 

Same exact brush/ stroke used on bother versions, sames scale on the screen. 

All the paint brush tool settings are exactly the same too (set to fully accurate under fidelity, same settings for edit selected paths with 6 pixels, fill brush strokes, etc). 

I can't figure out what I'm missing. 

I'm grateful for any help!