I think this is a bug in libhyphen 2.8.6: In the following example, this hyphenation is NOT found correctly (in fact, no hyphenation at all: 0000000000):
abendstern --> abend=stern
when the dictionary contains just these two patterns:
2d1s
end3sz
If the dictionary contains just the one pattern "2d1s", the correct hyphenation (0002100000) is returned. As far as I understand, the second pattern ("end3sz") should not even match, at least that is what the TeX program patgen thinks. So it should neither inhibit the first pattern ("2d1s").
Jens
Maybe the problem is that Hyphen uses modified Patgen patterns processed by Substrings.pl.