Hi Funkdigit , I had the exact same problem importing C4D data with DataPrep in 4.27.
I had C4DR24 and C4DR25 installed on the same PC as UE, but after uninstalling C4DR24, Dataprep imported successfully, so it could be a problem with C4D itself, if that helps.
Hold on! - Moz543 - I just re-read your reply - and bingo - I found I had an earlier install of C4D r24, and removing that has proven to be the answer.
I can even get .C4D files from my ageing r21 to import now to UE4 4.27.1
Cheers all - hopefully this little post might also help someone else in the future…
Thanks for the save with this one moz543. This is happened to me today with 4.27.2
In case anyone else runs into this - I had 4 other installs of C4D that hadn’t caused any problems. Right after I installed R25 is when my Dataprep objects began to freeze the Editor, after they had been working.
So after uninstalling all previous versions of C4D the Dataprep objects again work.