It doesn't have some sort of macrovision protection, perhaps?
Some of the USB devices have a "VCR" checkbox, in capture settings, which might make it more tolerant - have you got such an option?
Otherwise, I don't think you are going to get much improvement without trying new gear.
I have a 700 PCI and a S-VHS VCR. They can't cope with heavy drop outs, but normally dropped frames don't lead to OOS for more than a second or two.
As
you appear to live in the UK (timezone GMT?), I'd be happy to have a go at capturing the tape
for you, as long as you are willing to meet the postage costs, but I can't promise anything.