How to fix code folding in monodevelop

Hi there.
In monodevelop there is a feature called code folding but sometimes it just doesnt work, the little plus/minus signs are missing from the margin. Does anyone know how to “fix” the code parsing or whatever it is thats causing code folding to disappear? I code in js.

Cheers
AaronC

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Here you can see, the OnEnable function is fine, but AssignNextItem() which is the last function in the script does not display these. The script compiles without errors