Fenix 7 crazy speed and distance

I suspect the problem you’re experiencing with the F6 is different to the OP’s. Look back through the F6 forum history and you’ll find many threads discussing the F6 GPS performance that predates the current public released version. That version was released a number of months ago so unlikely to be impacting your recent problem. 

Garmin support have come back telling me to contact my eBike manufaturer! ... WTAF!
The watch has been erased and factory reset ... four or five times now .... there is no eBike or connection to one.
So tonight I did another factory reset to be sure, kept all standard basic settings (no restore from backup or anything like that). I also deleted the device from Connect on my phone. Grabbed my other non-eBike, did over 40kms ... this is the result. 
At no stage during the ride did the asent or decent metrics change, locked at zero for 3 hours.
No idea where to go next  ........ I guess I now have an extremely expensive paper weight

You go back and keep pushing them!  Having taken the "e" out of "e-bike" , see what their next excuse is.  I would try some other activities - go for a run/walk and see what happens.  Install something like PSX-8 RawData that can show more of the raw sensor data.  There is also a diagnostic mode but you will need to do some googling to find out how to get into it.  Does the Activity Summary on the actual watch match the Garmin connect data?  I've generally found support to be decent once you get past the "did you try unplugging and plugging it back in" stage.

True originally but if I understand correctly, he has done a factory reset (one of many), then headed out on his non-ebike so unless whatever the LEV protocol is coming from got connected again something else is the problem  and it would not appear to be related to the ebike.  Also why it is suggested he try some other activities to "hopefully" get support to take a better look at things.  I guess another look at the latest fitfile might show something (again).