Power BI Tabular Editor - Format String Expression not calculating the same value as the Expression

Hi everyone,

i am currently facing a problem where I need to create a dynamic formatting in a calculation group. One decimal for values below 10 / above -10 and no decimals for everything else.

During development, this works like a charm for e.g. the following Expression / Format String Expression

I just use the same calculation in the format string expression and define the format based on the smaller 10, bigger -10 rule.

This works the same way if i just evaluate the selectedmeasure (in another calculation item):

Now for whatever reason, the same construct does not work for the following Format string expression:

The calculation inside the calc variable returns values when used in a expression or a measure (the measure KPI value calc used in the screenshot below is the Measure the SELECTEDMEASURE() statement has to evaluate):

During testing, I found out that the calculation you can see in the screenshot above returns a blank / 0 value (both statements individually have the same result) if used in a Format String Expression:

Now long story short, my questions:

• Why does the same calculation return blank in a format string expression but returns the correct values in a measure or expression?
• Why does this construct work for the first two cases, but not the third one?
• Is there a way  around this? I need to calculate the values in the format string expression to apply the correct formatting to the values.

Best regards and i wish you all a nice week!

Timo