Weird curling problem when printing a thin item in 100% infil

[TTVert]

The print job is a 4.5mm thick plate (lid actually) that is 155x160mm (See attached stl). It will curl on the front right side of the print when printing infills of 50% or greater. Al though due to time constraints I only tested in 20% (my normal go to infill), 50% and 100% (What my goal infill for this job was)

• The printer is a maker select 2 that I've had for many years.

• The bed surface material was replaced a few months ago also but not because of this, just because it was years old.

• I am using the same filament I've been using for 2 rolls from amazon (SUNLU).

• I've had no other issues w/ this filament and reviews have been good

• I print at 210/40C and always have w/o any issues

printer config:

• Maker Select 2

• I have a duct w/ a cage fan that cools prints. Print cooling fan is running after layer 2

• 210/40C

• 1st layer 15mm/sec

• all other layers 50mm/sec

• .28mm layer height

• 210/40C

print info and tests I've run on same job

• If I print the job at 50% infill it's better

• If I print the job at 20% infill it does not curl

• Tried to reduce printhead temp to 200, no change

• Bed is level to .001" as confirmed w/ a feeler gauge

• Bed is clear of any debris

I don't think it's pertinent here but I have included a copy of the item I was printing.
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