yes that temp is huge. my original error takes several hours to
get. so this test case is a much smaller pdb and mtz file.
at normal temp the error doesn't happen. but at high temp
it is the same behaviour as my large original data set.

That doesn't tell us anything - the error could be caused by any number of problems with the coordinates, and unless you're using unrealistic high temperatures for the original data set too, there is probably something else wrong with it. In general you need to send us the original data, parameter file, and log file if you want us to debug problems like this (please use bugs@phenix-online.org or help@phenix-online.org for this, especially if it's unpublished data). However, after reading Ralf's reply, I'm not sure if there is anything we can do if the problem is specific to simulated annealing.

and at high temp it doesn't crash in 1.5 but does crash in 1.6

This is a problem with version 1.5, not 1.6 - it should certainly not continue to run if the protein bonds have been exploded.

-Nat