Why are my captures with virtualdub suddenly not working?
 

For a while I was transferring VHS tapes through virtualdub with a DV Camera attached to a firewire expansion card. However, for some reason this has stopped working. It will work for about 30 seconds or so, then the timing graph will show nothing (as if it isn't being captured at all) followed by a wild sync offset, making the video nearly unwatchable for the time it is happening.
Furthermore, in the preview window, the preview simply can't keep up in Virtualdub2 (dipping down from the normal display rate of 60 fps down to single digits at times). In virtualdub(1), the preview hasn't even been able to display AT ALL for the longest time, and I have no idea why.
Could all of this be due to some sort of driver issue? This is the only thing I could think, as while the tapes I'm transferring are at times not in the BEST condition, I can't think of any of them being in "completely breaks the capturing software" state. For context, I'm using Windows 10 with a GT710 graphics card. Not great, but it should get the job done (right?) I have another graphics card I was using before (an AMD r5 240 iirc). Otherwise I seriously can't figure out what's wrong here. Maybe my installation is cursed or something!

I wouldn't be using VDub to capture DV. I'd be using Scenealyser. It's sole purpose in life is to capture DV.

I have been using WinDV to import DV from Canopus ADVC-110.

To update on what I've done and what's been happening, I decided to fully reinstall Windows 10 after realizing the original install was done for.
Upon reinstalling captures worked as they should, and I got several good captures out of it. However, upon installing the driver for my GT 710, for some reason the same issue started happening again. The firewire input would basically cut out after about 30 seconds, come back, Virtualdub would try to catch up, rinse and repeat.
I opted to disable the GT 710's Nvidia driver back to the basic display adapter, and while it worked for a while, when I came back to check on my capture about an hour later, the same issue had happened.
If I had to venture a guess, I'd say it's possibly a PCI-E bandwidth issue (the firewire card is in a PCI-E x1 slot)? Though I've never known the GT 710 to be a big bandwidth hog since it's not very powerful to start.
That or Windows 10 is just an awful OS. Regardless, if anyone has any more ideas, feel free to let me know about them, since trying to work around all of these things has gotten a bit annoying.

Have you tried the two programs suggested already? Most people doing DV capture don't use VirtualDub.

I'm not capturing actual DV (like DV tapes) with it. I'm capturing VHS tapes and just using a DV camera (well more realistically a digital8 camera) as a passthrough. Besides, I'm not sure how those programs would solve the issue. The best way to describe the issue is like the camera is being disconnected at pseudo-random times. Imagine someone just at any time randomly unplugging the firewire device for no reason.

You are, in fact, capturing DV as if it was from a DV camera. Once the analogue video goes into the camera, it is digitised and goes to the computer as DV via your Firewire cable.

I imagine that the camera would output a steady DV stream, regardless of the quality of the input.

As already suggested, I'd urge you to give Scenealyser or WinDV a go. They are proper DV capture programs. WinDV doesn't work for me on Win 10, but it does for others. Scenealyser works well. I have published a Scenealyser guide here.