500 error with map services

I'm using Essentials REST API version 4.14

Has anyone else been getting this error with map services?  It doesn't occur with our feature services.  We have a map service with a series of layers in it (maybe 5).  I try and filter one of the layers and it produces this 500 error in the browser console: 

GET https://bruweb.ems.tas.gov.au/Geocortex/Essentials/REST/sites/sites/Burn_Planning/map/mapservices/7/rest/services/x/output?u=https%3A%2F%2Fbru.ems.tas.gov.au%2Fserver%2Frest%2Fdirectories%2Farcgisoutput%2FBRU%2FBurn_Planning_MapServer%2F_ags_mapdc637412ee824f18a2dd8cfd53f657fb.png&h=nwTNFAXzUhuywtEdM8P62MluNDE&token=SK1sU71kCcskqm3oTo1iZdSgAARGveyJeGAkaAvuJmeV8iXgAANps7MKRDtUWEWxi5knmIN4hh 500

If I then turn one of the layers off in the group they all draw and the error goes away, if I then try and filter another layer it will again produce the error and I have to turn another layer off to get it to refresh.  The error is intermittent and occurs or doesn't occur in a variety of circumstances.  Once I know how though, I can easily reproduce at any point in time though.  

I found that if I import the same map service to a new map, the error occurs in the new map, but I found that if I create a new map and add the same map service layers in from the catalog (not import them) it doesn't reproduce this error.  

Anyone seen anything like this??  I have had no luck whatsoever with support.