Jan, I love your pictures!
No film has been subject of so much rumor and just plain bovine excreta as EFKE R25. It's a film. It's as close as it's possible to get to the old ADOX R25. But it's not a thick-emulsion film, and there's no voodoo necessary to use it.
It no more requires pre-wash than any other film on the market. But pre-wash is often a good idea anyhow, at least IMHO. It certainly doesn't hurt.
It has no extra gelatine layer that must be removed. There is nothing at all that must be removed, and the film needs no extra precautions.
Maybe the gummy residue was just that - excess sticker glue? The roll films are taped to the backing; it's quite possible they've had a minor accident with the tape...