Sophos XG 18.0.3 Active sync email problem

I'm having an issue since upgrading to v18.0.3 in that iOS users are unable to send emails with attachments. I have a case open with support (03814579) for over a month but I'm not getting anywhere with them.

I'm lead to understand this is related to NC-62805 that has been resolved with a workaround, but the fix hasn't solved my problem.

This is the error from the logs

[Wed May 05 14:48:04.709024 2021] [security2:error] [pid 8308:tid 140077967550208] [client ***.***.***.***:61980] [client ***.***.***.***] ModSecurity: Request body no files data length is larger than the configured limit (1048576).. Deny with code (413) [hostname "*****.co.uk"] [uri "/Microsoft-Server-ActiveSync"] [unique_id "YJKiFH8AAAEAACB01acAAAHS"]
[Wed May 5 14:48:04.010018 2021] timestamp="1620222484" srcip="***.***.***.***" localip="***.***.***.***" user="-" method="POST" statuscode="413" reason="-" extra="-" exceptions="SkipURLHardening, SkipFormHardeningMissingToken" duration="699157" url="/Microsoft-Server-ActiveSync" server="mail.es-llp.co.uk" referer="-" cookie="X-BackEndCookie=S-1-5-21-2996036336-3693598292-524934663-2947=u56Lnp2ejJqBzp2emZybz87SyZvGydLLxpzM0p2anpnSnsedycfHyZnOycrPgYHNz83O0s/J0s/Lq87MxcvIxc/M; ClientId=YRYOSWFMKEBCRUAZSHNQA" set-cookie="-" recvbytes="1051762" sentbytes="4713" protocol="HTTP/1.1" ctype="text/html" uagent="Apple-iPhone10C6/1805.199" querystring="?User=******&DeviceId=************&DeviceType=iPhone&Cmd=SendMail" websocket_scheme="-" websocket_protocol="-" websocket_key="-" websocket_version="-" ruleid="21"

This is the fix that was applied

XG230_WP02_SFOS 18.0.3 MR-3# psql -U nobody -d corporate -c "update tblwafsecurityprofile set sec_request_body_no_files_limit ="10485760" where id ="21";"
UPDATE 0
XG230_WP02_SFOS 18.0.3 MR-3# opcode waf_reconfig -t json -b '{"Entity": "waf_advanced_config", "Event": "UPDATE"}' -ds nosync
200 OK

The error shown on the iPhone is

Cannot Send Mail

The message was rejected by the server because it is too large

Can anybody suggest anything else?

Thanks