Hi Koivu,
Thanks for posting in our forum.
What's the version of your Windows system?
Could you please tell us more details about what you mean by "it will automatically reset my defaults for word and excel"?
If possible, you may share some screenshots about the issue via
OneDrive and paste a link here then we can understand better about your problem.
Besides, please try to repair Office via Control Panel and try setting the default again and see if there will be any improvement.
Best regards,
Yuki Sun
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