So if you edit "CareerOptions" file you need to edit "Flotillas" file too,
otherwise there coud be conflict and CTD. like this
...................................
"CareerOptions" file
[CareerOptions 1]
ID= TotalGermany39
[CareerOptions 1.Flotilla 1]
ID= C1Flotilla1
NameDisplayable= 2. Unterseebootsflottille
IDLinkFlotilla= 2ndFlotilla ; link to ID in Flotilla upc file
IDLinkUserPlayerUnits= F2VIIB, 1 .. here was F2VIIA

FlotillaBriefingText=
FlotillaCommonality= 1
...................................
"Flotillas" file
[Flotilla 2.UserPlayerUnitType 1]
ID= F2VIIB .......was F2VIIA
NameDisplayable= Type VIIB U-boat .....was VIIA
AvailabilityInterval= NULL, 1941-01-01
IDLinkUserPlayerUnitType= VIIB .....was VIIA
UnitTypeCommonality= 4 ; to be used when a random choice is assigned
IDFlotillaLinkTransferTo= NULL
..................................
So Kromus maybe your "flotillas" file is edited like that too,
otherwise there could be a conflict . And thanks a lot for pointing me to
to this.