Report Accounts Receivable listing with GST

In Web Browser when I produce this report there is list variation between GL and AR Module of positive $103.50 but if I use desktop the Accounts Receivable with GST report shows a variation of negative $1138.50.

Undertaking a tickoff I have isolated it to a single client.

In the Web Browser report this client has a negative balance $103.50 in its account but it is not listed.

In the Desktop report this client is listed as negative balance $1242.00 when it should be a negative $103.50. The value of the clients recurring invoice is $1242 (12 instalments $103.50 are receipted post invoice issue) which is not processed until after month end. The Browser appears to be presuming the instalments precede the invoice to be issued and not related to last years invoice. 

Desktop negative 1242.00 v Web Browser positive 103.50 gives variance = negative 1138.50. WHY?

My expectation is that the same system should not be producing differing reports which have been produced within 10 minutes of each other for the same specified date being previous month end.

Would appreciate a call from MYOB support to help me understand why the variances arise.

Anyone else having this experience?