I'm using SDL Studio 2021 Professional (SDL Trados Studio 2021 SR1 - 16.1.3.4096) - and keep hitting a problem with references

I have a lot of references where the Article no. (Austrian Paragraf) or para. is in the form 1a, 1b, 1c, 1d.

These numbers are recognised as placeables but for values of less than 10, as soon as I add an empty space they are converted to upper case. 

E.g. para. 4a gets changed to para. 4A.

Have I missed some simple setting that kicks in for two character words that is somehow also changing placeables?

Thanks in advance,

Michael