BG1/IWD-style proficiency causes the core Mode 2 randomiser component to fail (and probably Mode 1 as well..). More information here: https://www.gibberlings3.net/forums/topic/36607-bug-error-cannot-convert-rcp_prof-to-an-integer-v7-win/ and here: https://www.gibberlings3.net/forums/topic/31667-errors-during-linux-install-cannot-convert-rcp_prof_/
BG1/IWD-style proficiency causes the core Mode 2 randomiser component to fail (and probably Mode 1 as well..).
More information here: https://www.gibberlings3.net/forums/topic/36607-bug-error-cannot-convert-rcp_prof-to-an-integer-v7-win/ and here: https://www.gibberlings3.net/forums/topic/31667-errors-during-linux-install-cannot-convert-rcp_prof_/