What's causing these inconsistent blotches and failed layering?

[ConnorB5338 0]

Hello there,

I am printing on a Ultimaker 3, 0.4 Nozzle, 0.15 layer height with White Ultimaker PLA at 205C. (This problem is also happening on our Ultimaker 2's where i work)

I'm experiencing these inconsistent and ugly finishes on the primarily inside perimeter of prints (Please see attached). These inconsistencies seem to be happening randomly and i have little idea what could be causing them.

The other picture shows bridging which looks to be bad adhesion to the previous layer. Any idea for things to investigate to get this to stop happening?

My only guess is that although we try to stop it, we have sometimes run abrasive filament through these nozzles. Is a damaged nozzle something that could be causing these type of blobs on the inside perimeter of shapes?

Thanks for the help!

[Nicolinux 287]

Do you use Cura to slice? If yes, take a look at the "Layer preview" (top right) and enable "show travels". If the dark blue lines coincide with the blobs on the inside, then we can try to debug that.