Anyone has RSUs that are taxed abroad?

Using an accountant for the first time to help with self assessment as I was given RSUs.

These are included as income but are taxed on vesting via witholding shares (so eg. if 20 shares vested, they were shown as income but my account received roughly half of these).

Accountant doesn't think these should attract any relief (or hasn't realised how they are being treated - unsure). I believe they would. Anyone has any experience of this? Is contacting HMRC worth it?