I have had this dozens of times, and found where the problem lies. It happens with plugins of which both a VST2 and VST3 version are installed, and which are not coded to be different. Both VST2 and VST3 in these cases use the same name and same ID.
The advantage is, that when you used a VST3 and remove it, it will load the VST2 version. But somehow, S1 mixes the codebases resulting in random crashes. Mainly at opening a project.
Simple solution is to remove the VST3 version of these double plugins. They are easy to find, as in the plugin manager, there is only a VST3 version shown of these. The VST2 version is hidden because it's aliased/mirrored by the VST3 version.
The VST plugins that work correctly and have no issues in S1 show up in the plugin manager as both VST2 and VST3 version. But if you used the VST3 version and remove it in this case, it will not find the plugin as the VST2 has a different ID and hence is not the same plugin.
If you have removed any double VST2 or VST3, you need to remove the plugin config and do a full scan, as they are cached.