Move contacts to gmail using em client

I’m in em client moving all of my contacts from my local contacts folder into my gmail account so i can view them on other devices.  When i move them into to my gmail contacts folder (select, click and drag) all appear to have moved successfully however only some of them can be seen on other devices.
Each time this has happened, an error occurred in the em client midway through the move:
 “An Error Occurred - specified method not supported”. 
After the error, all the contacts do appear in the em client under my gmail account however, other devices can only see some of them… as though the error has interrupted the upload at some point.

This does not occur if i move them 1 contact at a time.  Is there a limitation on this?  I have 100s of contacts to move so one at a time is not ideal!

Windows 10 PC running em client.  Phone - Google pixel.

Do you have any suggestions/have you seen this before?