I'm not sure what's happening here. I've tried to replicate the lag issue on multiple computers (both on Window & Mac computers) without any success and we've tried to diagnose what the issue could be but got the same result. There are a few more things I would recommend trying and see if they fix the issue. I've listed these below.
- Restart your computer. If it hasn't been shut down in a while it may need to be restarted to refresh the system.
- Reinstall Dynamic Components. In SketchUp 18 they made changes to Dynamic Components which may help fix this issue (it may also fix the Handrail Tool error I believe you've been having as well). To do this in SketchUp 18 & 19, go to 'Window > Extension Manager' and in the 'Manage' tab click the update button to update this extension. If you aren't able to you should be using the latest version.
- If you aren't already, update to the latest version of PlusSPec (v19.0). There were performance changes in this version which make the dialogs throughout PlusSpec open quicker.
If the above doesn't fix the issue, I've got a few questions which will hopefully help in diagnosing the error.
1) When does the lag happen? When the dialog is opened or when the changes are made (i.e. after Submit is pressed)?
2) How long is the lag (i.e. a few seconds, more than 10 seconds)?
3) Does the lag happen for every window or just specific ones?
4) Is the lag only when editing a window or door using the Edit Window/Door Tool or does it happen for the other window & door tools as well?
Please let me know how you go with the above recommendations.