To piggyback off this:

Not to be that guy, but I have an immediate family member who got their booster and (I don't remember what the technical term was, apologies) their immune system started attacking their nerves, which caused them to lose most control over their hands, arms, feet, and legs, and at the worst point, become bedridden and at risk of dying, had they not received the care they did (I've been told the docs said 'a few more days and it would have been too late'). They are recovering, still, almost 3y later; daily care, wheelchair, walker, weekly therapy. It's been a very slow process, and they only got the help they needed because another family member is in the medical field and was able to correctly diagnose their situation, when their main (prior, now) gp shrugged it off as the flu (???) twice, even as their condition was worsening and painfully obviously not just "the flu". I have heard of friends of friends who seem to have had this phenomenon occur, but were not as lucky to receive (the correct) treatment in time.

Two other family members who got the booster at the same time had no issues. I got mine a couple months after, with no issues. They are usually safe... but not always. Practicing medicine, studying science; never absolutes. Healthy dose of skepticism is okay. But weigh the risks logically, not just "this can happen so I'm never going to do X", as sometimes X can save you from Y. My mom in particular was freaking out when I got my booster - understandable, but it's one risk over another.

E: autocorrect shenanigans