o365 External Guests Cannot Access Shares.

When inviting guest user in o365 from a different tenet usernames show as username_their.domain#EXT#@mydomain.onmicrosoft.com login works fine, however folders/files shared with them are non accessible.

Their appears to be a loop when you access the shares trying to access

PROPFIND /remote.php/dav/files/username_their.domain HTTP/1.1" 241
GET /ocs/v2.php/apps/text/workspace?path=%2F HTTP/1.1" 142
PROPFIND /remote.php/dav/files/username_their.domain HTTP/1.1" 241
GET /ocs/v2.php/apps/text/workspace?path=%2F HTTP/1.1" 142
PROPFIND /remote.php/dav/files/username_their.domain HTTP/1.1" 241
GET /ocs/v2.php/apps/text/workspace?path=%2F HTTP/1.1" 142

...

Users that are synced from the local domain to 0365 work fine, as well as users created in the o365 environment, they appear to access

"PROPFIND /remote.php/dav/files/username@my.domain/Share HTTP/1.1" 595
"GET /ocs/v2.php/apps/text/workspace?path=%2FShare HTTP/1.1" 142

I am suspecting that the #EXT# is breaking the PROPFIND portion, is there a change I can make to my config to get the pulled in username to just show their email and not the current long username? Or does this require some kind of code fix?

No files or tests are named. Start by reproducing access with an O365 external guest and compare the logged WebDAV PROPFIND and OCS workspace requests for the long #EXT# username against a working user. Done means determining whether the identity format requires configuration or a code change and restoring access to shared files.