If this computer has been upgraded several times to newer versions over the years and now macOS Big Sur , the computer maybe experiencing the the affect of the upgrades and any older Third Party Application installations / removals.
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The final word from Apple on Managing the " Other " Category
Other: Contains files that don’t fall into the categories listed here. This category primarily includes files and data used by the system, such as log files, caches, VM files, and other runtime system resources. Also included are temporary files, fonts, app support files, and plug-ins. You can't manage the contents of this category. The contents are managed by macOS, and the category varies in size depending on the current state of your Mac.
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