UTF8 Replacement bytes "EFBFBD" in Revert error reason

Unable to decode the revert error from Simulation (and probably from real txs too).

What I've noticed when I decode the revert string to HEX, is that it contains a lot of "EFBFBD" bytes:

"EFBFBD" is used as a standard UTF8 replacement bytes if the source byte cannot be encoded into UTF8:
https://blog.gdssecurity.com/labs/2015/2/18/when-efbfbd-and-friends-come-knocking-observations-of-byte-a.html

As you can see it couldn't encode 9C.

If you replace EFBFBD with any random byte (like "FF") - then you have a proper length ABI-Encoded custom error (with 4 bytes in the beginning, and 32+32 bytes two uints after).

I'm not sure where this replacement happens - on the Ethers side (in fetchJson they use toUTF8 encoding) or on Flashbots Relay side.

But if it happens on Ether's side - maybe we can use another connector?