Visual errors while using UDF in conditional formatting on Excel 2016 32-bit

Dear friends, Excel fans,

I have a strange problem with displaying in Excel 2016 32-bit if any UDF is used in conditional formatting. I have an Excel spreadsheet that works as a form in which I have about 70 conditional formatting objects and I have one UDF, which I found necessary for these CF.

I personally use Excel 2016 64-bit where is no problem. But as soon as I try any 32-bit Excel 2016, visual errors start - the text is accidentally disappearing. Best to see on screenshots below:
- the first is 64-bit - it looks exactly as I need it
- the second is 32-bit - some of font missing = visual errors

Since there is no build-in option for transparent font (at least I don't know any), I can say that the font color is displayed same as the background color. But why?

It has these mysteries for me for which I can't even start to properly search for solution:

1. it is only a pure visual error - no properties has been changed (Range.DisplayFormat.Font.Color, Range.Font.Color - still the same)
2. exactly such effect (i.e. the font changes color to the background color) I used in all my conditional formattings - but - this effect also happens in cells where is no conditional formatting at all (!) - so we can say that the effects of conditional formatting appears completely independent from the rules for them
3. visual errors are refreshed/changed just by scrolling the view - not by clicking, not by changing the content of cell / sheet
4. its irrelevant how the UDF is written - it can also be quite simple e.g.
   
   

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   the behavior is still the same
5. I don't see any memory consumption fluctuations - there was at least 4GB of memory on each PC with 32-bit Excel, excel consumed max 0.5GB, no hard faults

I tried to:

• test on 3 PCs (win 7 64-bit, win 7 32-bit, win 10 64-bit) = everywhere the same
• delete the rest of entire VBA code except the one UDF = no change
• delete all cells where I call functions, whether UDF or default = no change
• delete even for sure all names, all other sheets = no change
• disable ScreenUpdating, EnableEvents = no change
• disable animations (via Ease of Access Center) = no change

Finally if I delete that one UDF I use in CF, all visual errors will disappear (!). The same if I turn calculations to manual, everything is fine. This proves to me that once I put any UDF to any CF on Excel 2016 32-bit, calculation of such UDF in CF causes visual errors.

Please:

• have you ever encountered such a problem?
• do you have an idea for some VBA solution to this problem?

I will be glad to add any missing information, please let me know what I forgot to mention.
Thank you

Marek, Slovakia