"i am try to reinstall monterey on my macbook pro keep getting the error buildinfo. preflight. error error 21: [...]My MacBook Pro has run out of space. System data takes up 857.35 gb!![...]"
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Clear Space:
Your Mac is about to stall, and will potentially overheat. So, you need to clear space. You're not gonna clear "Other" 100%. So, from here, clear Other the best you can. Here is what Google Recommends: To clear the other category of storage on Mac. The only ultimate way to clear "Other" in-fill, is to back up your Mac using Time Machine Backup, and then format your derive, and then migrate items from the backup using Migration Assistant. Items such as apps will need to be reinstalled, manually. So, contact the Developer, requesting a new license to get it reinstalled.