@ Dan Parker
Thanks for contacting us.
Would you try disabling the following components one by one and track the behaviour:
-JustCode's Visual Hints (JustCode menu\ Options\Code Analysis\Hints - all checkboxes to be unchecked.
-JustCode menu\ Options\Visual Features, and JustCode Options\Visual Features\Structural Highlighting.
-Typing Assistance (JustCode \Options\Typing Assistance) and see after that whether you will have the same issues with JustCode? Just to make sure that those are not at fault in your environments.
Please, send us your logs located at %localappdata%\JustCode\Logs. Maybe there is something unusual.
All the best,
the Telerik team