VariantToJSON - Now not working

WDv22 - 01A220063m

Yesterday this was working fine.
Only thing that has changed is that M$ applied the 'creators update' without so much as a by your leave.

I have a multi-select looper, on save I loop through this and add each selected row to an array and execute the following code.

//If selections have been made
IF ArrayCount(clMatching.m_ArrEssentials) > 0 THEN
	//Store the array content
	lvArrContent = clMatching.m_ArrEssentials
	//Update match string with the all selections as JSON
	clMatching.SET_JSONEssentials = VariantToJSON(lvArrContent)
END

Yesterday no problem - today I get the fatal error.....

Error at line 17 of Click btnSave process.
VariantToJSON function called.
The JSON serialization does not allow the 'object' elements.

My understanding that it is supposed to do exactly what the error says it cannot.

I assume that 'object' is referring to the class - I have tried this as a class Property and class Method but get the same error.

Yesterday it saved it as [ { "nID":142 }, { "nID":143 }, { "nID":144 } ]

Any thoughts