I got a leak on my shimano 105 R7020 STI My caliper rotor push oil back in the STI. All of the sudden mineral oil started leaking.
Do you know SKU of this part?
According to the ST-7020R exploded diagram at
https://dassets.shimano.com/content/dam/global/cg1SHICCycling/final/ev/ev/EV-ST-R7020-4341C.pdf
That part doesn't exist as a removable part, hence why you need to confirm your exact shifter part number.


For completeness - the dealer manual is at https://si.shimano.com/api/publish/storage/pdf/en/dm/RADBR01/DM-RADBR01-07-ENG.pdf
and a browse through shows no mention of removing that plate.