Something is very wrong here.

Is it possible that the longer bolts are too long and somehow bottoming before they tighten?

Also, the precession I referred to earlier, related to chainring movement, not the bolts themselves. Using a threadlocker may help keep the bolts from loosening, but won't address the core issue. You need to increase the friction between the rings and tabs of the crank spider, so they can't shift under chain load.

Obviously tighter bolts can be a part of that, but you seem to be hitting the limits. So, start with an absolutely dry interface, (solvent clean, and dry). If that isn't enough, use my lapping compound suggestion, or apply an anaerobic adhesive, like a bearing retaining grade, between the rings and tabs. There are also anaerobics that swell as they dry, so applying one along the boundary between the chainring and crank shoulders may prevent the precession.