Random failures/time outs on drone cloud

We’re trying to use drone cloud for github.com/flang-compiler/f18 and it seems to work well most of the time, however sometimes we get failures or timeouts that I can’t understand the origin of.

You can see for example in this build https://cloud.drone.io/flang-compiler/f18/1/4/2 that in the arm64-gcc pipeline we get a failure because gcc was killed. Initially I thought these were out of memory errors but I don’t think we can be hitting the memory limit on these systems (even though are compiles are memory intensive.

Any ideas what might be causing this?