Mal de debarquement
 

Has anyone ever suffered with this and is it a class 1 show stopper?

not too much info about it on the net!

Quite a bit ... but not necessarily in English.

https://rarediseases.org/rare-diseases/mal-de-debarquement/
https://vestibular.org/article/diagn...-debarquement/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5764463/
https://www.mountsinai.org/about/new...-syndrome-mdds
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6240763/
https://mddsfoundation.org/fr/ - perhaps DeepL or Google Translate will be your new best buddy for the foreign language sites ;-)

I know very little about it but feelings of movement can be normal and this sydrome is restricted for people where the symptoms last for more than 48 hours. I would have thought that anyone with such a condition would not want to fly regularly so my only advice is to check the diagnosis has been correctly made. If not, the individual doesnt have it!!!