Series 2A engine cutting out on downhill - when hot?

New to the forum and looking for advice.

My series 2 (1963 SWB) starts well from cold, idles fine but after driving for 5-10 minutes finding the engine cutting out particularly on downhill stretches.
(It has been hot September temperatures). It then will not restart until it’s cools down and runs again for 5 minutes before repeating the performance!

Got sparks to plugs, fuel appears to be getting to through. Any ideas?

Many thanks in advance.

Overheating coil?..

Thanks for the suggestion - is the remedy just to replace this part?

Youtube overheating coil there are tests you can do...when it cuts out have you tested for spark while engine is still hot...