Levinson 23.5 needs help.....

Need your help....
I just bought & used RCA-Camac adapters( from ebay) connected to my Levinson 23.5.
Anyway, now I don't know how to remove them from 23.5, seemingly tightly locked.
I asked the seller and he said the outer RCA end can be screwed off then the Camac end of the adapter can be pulled out directly easily.
I screwed off the outer RCA end but the Camac end seemed still tightly locked to 23.5.
How to remove this ?
I dare not pull out with big strength directly, afraid of causing any damage on either the end of 23.5 or that of the adapter.
Could you help?

Thank you!