Inserted frames from Hauppage, not VC500?
 

I have been having FITS trying to capture a tape where I get no dropped frames but in 90 minutes I get 300 inserted frames.
Needless to say the A/V sync is way off.
Setup is/was S7800U>ES-15>TBC-1000>Hauppage WinTV50>Windows 10.
Tried both with and without the ES-10.
Tried it in my Sharp VC-S101.
Not until I switched my dongle to the Diamond THEN only 2 inserted frames (so far).
Just sharing the experience.

Have you tried setting the process priority to high or realtime? I've found it can often be helpful.

If you're getting them behind the combination of es10 and tbc-1000 it would suggest it's something on the computer end causing problems.

Note that it's possible to tell virtualdub not to insert frames in the options if it's a big problem, but getting them tends to suggest either the source is unstable or something is giving the computer trouble.

It is an old tape (aren't they all), and using the Diamond I got 3 inserted frames in 53 minutes, much better.
As for my computer, I shut off AVG and unplugged the internet before, but only changing the dongle made a difference.