It's the overhang. You will get best results with more fan. And then try more fan. And then more. For example maybe a house fan. The first step should be to rotate the frog such that it is facing to the left because that is where the UMO fan is and the UM2 has a fan closer to the nozzle there.
Also lowering temps can help. What is your current layer height and printing temp and speed? I would slow things down to maybe 20mm/sec and maybe 190C to get better results on that overhang. Overhangs like this are very tricky. Another frog model that is looking up more such that the overhang is more vertical would help a lot!
Can you tell us what settings you have used and which Ultimaker?
Do you also have a picture of its belly?
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