I 've downloaded the ADF again, but it is still the US Version. Is there a key to change mode?
On the Japanese version, a Barrel cannot drop down a ladder while Jumpman is on it (upper third).
The change form SUBQ.B #4,D0 to SUB.B #$10,D0 make this possible. You can compare the MAME ROMS to check it.
// original Z80 assembly code of the subroutine US Ver.
2178 3A4863 LD A,(#6348) ; get status of the oil can fire
217B A7 AND A ; is the fire lit ?
217C CAB221 JP Z,#21B2 ; no, always take ladders before oil is lit
217F 3A0562 LD A,(#6205) ; else load A with Mario's Y position + 5
2182 D604 SUB #04 ; subtract 4
2184 BA CP D ; is the barrel already below or same level as Mario ?
2185 D8 RET C ; yes, return without taking ladder