DaVinci Resolve 15.0b2 still crashing at export (alpha chan)

Hello
DR15 is still crashing even with the Beta2 when attempting to export a (even little) video WITH alpha channel. It crashes as soon as we click on the Render button. It doesn't seem to crash with no alpha channel asked.
We still can't export alpha channel using the rushes we use (AJA recorder). This was not fixed with all the DR14 releases (no answer from the Tech support at all, still waiting for one...). This is a main bug we'd like to be fixed too please because it makes keying totally unsable.
Btw, DR has become VERY slow to launch... Normal?
DR15 is still crashing even with the Beta2 when attempting to export a (even little) video WITH alpha channel. It crashes as soon as we click on the Render button. It doesn't seem to crash with no alpha channel asked.
We still can't export alpha channel using the rushes we use (AJA recorder). This was not fixed with all the DR14 releases (no answer from the Tech support at all, still waiting for one...). This is a main bug we'd like to be fixed too please because it makes keying totally unsable.
Btw, DR has become VERY slow to launch... Normal?