Houdini 6 and Syzygy

[MOBMAT]

I found a few positions that Houdini 6 can't solve when Syzygy tables are enabled.
Conditions are H6 Pro, 16384Mb hash, 4 threads, Tactical mode (makes no difference), Syzygy on, Nalimov (on or off)
Syzygy Probe Depth 20 (default)

I verified the checksums of the Syzygy files.

This is a mate in 10, but H6 maxes out depth 99 and says M11.
[d]k1N4n/P7/P7/P7/P7/P7/1PK5/8 w - - 0 1

If I disable Syzygy, and try it without any EGTB or with just Nalimov enabled, it finds it easily.

Here is another, a mate in 9. H6 reports a Syzygy winning score (+148.96), but never resolves the mate.

[d]k7/8/PP6/K7/4p3/2Rp4/2r5/8 w - - 0 1

Any ideas what is happening here?