Configuration > Scanning Options > Service Options section >
'Computer Threads' = set to 1
'IP Threads' = set to 1
Though if I were you I'd submit a request for the IDS/IPS to allow the LS scan server IP - that's the first thing I do when implementing LS - document and make a case for the software, present to security team, get the exception.
If they want granular you can submit for allow the specific ports LS talks on
https://www.lansweeper.com/knowledgebase/used-tcp-ports/