Hi ,
If possible, try another tape to see if that works OK and that it is not a faulty tape.
If still no good then perhaps the heads are dirty and need to be cleaned. Search online for a ''JVC GR-303U head cleaning tape''
[https://www.ebay.com/itm/1-Sony-DA30-Mini-DV-head-cleaning-tape-for-JVC-GR-DA30-D850-D870-D796-D30-D33-/302578771808|This] is an example only to show what it may cost. I’m not sure if it is suitable for your particular model but it will be similar. Verify with the seller first if you can’t find another one online.