Usual preface, I’m with PreciseBits so while I try to only post general information take everything I say with the understanding that I have a bias.
Normally I’d look at runout first with a break in plunge, especially at very conservative feeds. However, it doesn’t look like you were having issues with other metals and smaller tooling so it’s not as likely. Then I saw this…
Assuming that’s not a typo it’s most likely your problem. 6062 contains lead and bismuth (for increased machinability). These types of grades were intended for aggressive cutting on high rigidity machines. So the “increased machinability” can actually hurt you if you can’t take advantage of it.
If memory serves, it wants a much higher chipload or is likely to gum up. Cutting the plunge depth will help but honestly you’re probably better off switching to another alloy (even more so if this is for jewelry and it’s going to be in constant human contact). Straight plunges are especially bad as you are typically at a low chipload and functionally dwelling for a time at the end of the plunge. If you need to keep using the alloy I would keep the plunge depth low, increase the feed, and ramp into the cut. Can’t really be more specific than that as I don’t have the feed/speeds or tool data.
Hope that’s useful. Let me know if there’s something I can help with or expand on.