I've rebuilt my ROM collection for the XML data from 0.173 with QMC2's ROMAlyzer (ROM Collection Rebuilder) yesterday. The result is perfect, that is, I see no issue in MAME.

Regarding your specific problem... well, yeah, "merging sets" by just copying files from parents will not work correctly. I'm not sure how you did it, but when it was done through CMP, the bug probably lies in CMP.

Anyway, when I instruct QMC2 to export "self-contained" sets (which is what CMP calls "merged"), the result is also correct here:

Code:
rene@marvin:~/src/mame-git> unzip -vl /home/games/mame/export/roadblstgu.zip | grep 7a29dc07
    8192  Defl:N     4069  50% 2016-04-30 09:07 7a29dc07  136032.107.b2

rene@marvin:~/src/mame-git> ./mame64 -rompath /home/games/mame/export -verifyroms roadblstgu
romset roadblstgu [roadblst] is good
1 romsets found, 1 were OK.


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