Thanks for your reply, Ken.
direction switch / jack : I'm using a standard Serge gate signals to drive the direction jack, so not really weak (0-5V). The direction jack is wired to UD and the top contact of the switch to SW, following the instructions. The center contact of the switch receive +15V. Nothing wired to the bottom contact.
I just noticed the direction jack works in forward mode if I send negative gate signals to it. But then it won't work in reverse mode (opposite to what I described in my original post)
Should I try to switch the cables going to UD and SW and see what happens ?
Regarding the reset issue in reverse mode, I checked the parts you said, the 547 is placed following the silkscreen, the associated diodes are placed correctly and behave normally when tested. I have no way to test the pinout on the transistor though (my transistor tester doesn't work any longer apparently). But it comes from the same batch than the 8 others controlling the led and gate outputs, which are behaving correctly, so I doubt the problem come from it. I also tried to swap it for another 547, but with the same results
All the resistors values are conform to the instructions.
Any other suggestion welcome, running out of ideas here ;-)
Thanks !
Philippe