Problem with multisystem unit (vcr)

[monks19]

Hi, for some times now, I bought a Panasonic (AG-W3) multi system vcr. Playing NTSC vhs, no problem. Playing/converting SECAM vhs, it's a nightmare (see the test file attached to this message). This seems to happen only when the unit's internal converter kicks in during playback, despite the use of a Datavideo TBC-1000 that I just aquired and seems to work fine on NTSC vhs. Otherwise, the use of NTSC vhs seems to be fine with the AG-W3.

I was wondering what can cause this ? Is it fixable ?

Thanks to answer