I use this on my SXT LTE6 Device
This is how I have got round it.
1/ Create System Script to Disable then Re-enable the SMS Receiving
2/ Setup Schedule (SMS-Reset) to run at boot and subsequently every 5 mins thereafter
/system script
add dont-require-permissions=no name=sms-reset owner=admin policy=\
ftp,reboot,read,write,policy,test,password,sniff,sensitive,romon source="#\ this is required to receive SMS messages as bug found\r\
\n/tool sms set receive-enabled=no port=lte1 \r\
\n:delay 2s\r\
\n/tool sms set receive-enabled=yes port=lte1 secret=MySecret\r\
\n:delay 2s\r\
\n"
/system scheduler
add interval=5m name=SMS-Reset on-event=sms-reset policy=\
ftp,reboot,read,write,policy,test,password,sniff,sensitive,romon \
start-time=startup
Not ideal, but it works.