Differences between mips64 buildds?

Hi,

I am observing "random" pytest failures when building one of my packages 
(astropy) [1]. This seems hardware related, since the test passes well 
on some buildds (osuosl-02, osuosl-04), while it fails on other buildds 
(osuosl-03, osuosl-05). Checking the buildd info for these machines [2, 
3] show however no relevant differences; both are Quad Core Loongson 
3A3000 CPUs; with 12 GB or 16 GB RAM, from the same sponsor, and also 
(in the latest case) running the same kernel version.

I am now wondering what the differences between these machines are, what 
the cause for these failures may be and what the proper handling of 
these failures would be. Can/shall one pin the build to a specific set 
of buildds that are known to work? Or just giveback the builds until 
they succeed? Or is this something upstream can/should fix?

Please Cc me in the answer, because I am not subscribed to the list.

Best

Ole

[1] https://buildd.debian.org/status/logs.php?pkg=astropy&arch=mips64el
[2] https://db.debian.org/machines.cgi?host=mipsel-osuosl-04
[3] https://db.debian.org/machines.cgi?host=mipsel-osuosl-05