There are several reasons for this kind of behavior of the site piping:

1. The piping model does not reflect the site condition, or visa versa.
2. The piping model is not correct to reflect the actual scenario. This requires an expert pipe stress engineer to verify.
3. The piping model weights of valves are different than the actual weights. Use the correct weights in the model.
4. The densities used in the pipe model are not correct. Check model.
5. If the model is absolutely correct the spring rates of hangers might be higher than the model requires. Check model and the installed hanger rates.

This diameter pipe and pressures require heavy valves, and I would expect they were supposed to be supported on both sides. The model does not show this on some valves. This may be manipulating the expected behavior of the piping.