Strange bubbling layers

Hey everybody. I am new to the forum and to 3d printing. I have had my Taz 6 for about 3 weeks and probably have about 100 hours on it. I’ve experimented with various filaments and had some great results and some not so great. The prints I’m doing will be mostly for commercial use so I’ve been primarily using ABS for many of my prints. I have worked out most of the bugs and am getting consistently good prints except for one issue that I haven’t been able to track down. About a 1/4" off the bed I will get about 10 to 15 layers of “bubbly” prints. It’s not even consistent all the way around, it’s only about half of the perimeter and it’s on all locations of the bed. The rest of the print is very very good. So what gives? I’ve messed with extrusion rate, z offset, retraction and z hop and can’t figure this out. Below are some photos. The pic with 2 pieces next to each other were different prints from different days with basically the same settings, except a few minor changes. The three that are on the bed still all had this issue in the exact same spot. Any ideas?

My profile looks like:
Layer height - 0.25
Shell thickness - 2mm
Retraction enabled
Bottom/top thickness - 2mm
Fill - 25%
Perimeters before infill - yes
Print speed - 50mm/s
Nozzle Temp - 240
Bed Temp - 110
Filament daim - 2.85
Flow - 95%
Retraction - 10mm/s
Retraction distance - 1mm
Initial layer thickness - 0.425mm - Cura always defaults to this but this is too big for a .5mm nozzle correct?
Initial layer line width - 125%
Speeds:
Travel - 175
Bottom layer - 20
Infill speed - 55
Top/bottom speed - 45
Outer shell - 40
Inner shell - 50
Fans - off

On an unrelated note, why does my LCD screen read “Sleep…” at random times in the middle of prints while it’s still clearly printing?

Thanks for any help!

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That looks like insufficient cooling to me. The print is not cooled quite enough which makes the thin overhang curl upwards. Then on the next layer the nozzle hits the curled up layer. This continues until it levels off after the overhang. I would try to add just a touch more cooling fan atleast when you are printing the overhang. You should not add too much though as ABS starts to crack between layers if it is cooled too much.

It also looks like you have a bit of banding on the vectical walls. I suspect if you wiggle the Z-axis leadscrews, one of them is a bit loose and wiggles side to side. I had that issue and all that was needed was loosening up the green mount that holds the screw on the bottom, pushing it upwards and retightening the screws. After that it was rock solid and no banding.