If it has been in use for some years, and shows no signs of heat stress or damage I might be inclined to accept continued use "as is"

Ongoing temperature monitoring by means of temperature sensitive labels might be prudent.

Good shout on the labels: I believe the cables are oversized for volt drop so shouldn’t get anywhere near a limiting temperature unless something’s awry

If there is no other reason to doubt the quality of the crimping, letting sleeping dogs lie is probably sensible. The problem with mixed metal crimps is oxidation/ corrosion  and eventually going high resistance, and to that end there are various grease-type compounds designed to limit the ingress of oxygen and moisture. The reason for the multiple bands of crimping is to reduce the risk of this occurring prematurely, and some makers specify a defined crimping order from the outside (cable end) inwards  (towards the termination) so that the outer crimp is almost sacrificial, and mostly holds the wire still for the later ones that do the electrical contact, and any compound is squeezed sequentially forwards towards the weep hole - assuming there is one, so that voids are full but metal touches metal.
Unless it starts to run hot, then adding extra crimps in the middle of existing ones, which may unseat the existing seal lines or push compound about like a hydraulic ram, reopening the joint, can cause more trouble than it solves.
To remove the ends and re-crimp sounds like it is impractical, and when it finally fails an underground joint will be needed.

Again monitor and inspect, but leave well alone.

Mike.

Thanks Mike; useful advice.

For the record the lugs themselves are bimetallic, so it's aluminium on alumium within the barrel. Not that that takes away from your point regarding oxidation.