Guess what?
MD5 value is ok in the file... MD5 string was wrongly defined in captital letters in es_bios.xml.
Fixed the string to lower. Now warning message is not shown but any PSX game I load, it just kick me out (just as before)...

Hi, I'm having the same error message.
I already have all psx bios. The only one is still missing is SCPH101.BIN which it is not included in BIOS_Recalbox_4.1_18.02.09.
I've found that file in serveral sites but always the MD5 is wrong as per what Recalbox need: 6E3735FF4C7DC899EE98981385F6F3D0.
Any clue?