just to clarify that your versions are what you have been told they are.
I’m assuming you are in an NTSC country
Are you playing vhs’ through a box that can handle pal VHS tapes? If you are, then great, if you are just playing it in a good old fashioned VHS machine, than, it shouldn’t be able to play a PAL tape.
The fact that it is playing a PAL vhs, has me wondering if the tape is a PAL converted to NTSC, and that is why it is playing on your tv.
As far as i know, you shouldn’t be able to play a PAL vhs tape on an NTSC machine, in an NTSC country, and see a picture on an NTSC TV.
Try setting your decklink to NTSC and run the PAL tape through it.
Glenn