Are you running an AMD CPU? I find the line weights change like you say the most when using break line command. If when using a basic command like break line and the snap indicators aren't showing - back out of the command and then re open it to keep the line weights from changing. This helps in my experience.
I've had projects that have upwards of 15 plan views eventually opened because of this issue. I have an AMD machine.
I just ordered a new tower with Intel processors and don't expect to have the same issue.
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Tylor Foster
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