METIS_PartGraphKway fails to respect allowed load-imbalance with Metis 5.1

Dear professor Karypis,

I am using your great software since a long time in my code.
It is a really great product and I am really satisfied by its performance and stability.
Recently, I have moved from version 4 to version 5.1 of Metis.
Most of the time, it gives decomposition as good as previous version and allow to treat bigger graphs thanks to better memory management which is great.

Unfortunalely, sometimes, I observed that it is like it fails to decompose respecting the load-imbalance given thru the ubvec vector.
Generally, I use multi-constraints with a value of 1.001 for the first one, and values between 1.05 and 1.10 for the others (between 1 and 4 constraints depending on options used).
When I compute the different weights of each partition after calling METIS_PartGraphKway I notice they are all good except for 1 or few of them for which I observe up to 30% imbalance resulting in a very poor performance of the solver afterwards.
I never observed such behavior with previous Metis version.

Is it something you are already aware?

Do you have some recommendation to avoid such behavior?

Thanks a lot for your kind help,

Eric.