I've used one roll of Efke 100 in 127 (yeah, I know, small sample) and had no trouble, even with sunlight falling directly on the (light amber) window on several occasions.
I've gotten the impression that Efke got hold of *one* batch of bad paper, but due to warhousing practices it keeps popping up on current dated film from time to time.
However, I've been recutting 120 to 127, which works very well if you have spools -- I found reversing the film while respooling lets me use the 6x4.5 track for 4x4 and the 6x6 track for 4x6.5 (that one requires masking the camera a little) but this way I get a huge selection of emulsions...