SUMMARY
***
Incorrect Currency Conversion in Reports 
***
Transaction reports of foreign currency transactions (dividends in my case) do not work as intended. Selecting "Convert Values to base Currency" corrupts values and provides erroneous totals (which should not bethere since the reports contains mixed currencies). NOT selecting  "Convert Values to base Currency" DOES convert values into the base currency with correct values & totals (and a nuisance currency code before each value when their all in the base currency. An inability to report accurately invalidates storing the data.

STEPS TO REPRODUCE
1. Create a foreign currency dividend
2. Run the report "Transactions by Category"
3. Tick the box "Convert Values to base Currency"

OBSERVED RESULT
The report of foreign values are wrong and not converted to the base currency

EXPECTED RESULT
Foreign values should be converted to the base currency

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
kmymoney: 5.1.1-ad14462
Linux/KDE Plasma: opensuse 15.2 
(available in About System)
KDE Plasma Version: 15.8.6
KDE Frameworks Version: 5.71.0
Qt Version: 5.12.7

ADDITIONAL INFORMATION
This is a variation of bug 419519 in Vn 5.0.8
Do NOT tick the "Convert Values to base Currency" box & foreign values WILL be converted to base currency (and totalled correctly).
DO tick "Convert Values to base Currency" & random wrong values appear with erroneous totals.