record and watch different channels

hello,
I have VU+Duo2 with 4 tuners.
Provider is TV Vlaanderen through a CI+ module - CAM701 (viaccess-orca).
The tuners are all working, I tested that.
I try now to make a recording and watch another channel at the same time.
When the recording has started on one tuner, and I select a different channel for watching, I see that a second tuner jumps in correctly but there is no image, unless the channel is of the same polarisation as the one being recorded.
I tried setup of Oscam but with no result. The card shows as not ok, no entitlements, which is probably because it is a CI+ module.
I cannot remove the card because it is integrated in the CI+ module.
Can someone help me please? Thanks.