in vanilla bundles can be nested inside each other, however the nested bundle has a "weight" of all of the items it contains +4 as to not allow for infinite storage. these bundles have a fixed weight of 64, allowing for infinite bundle nesting and in turn infinite storage
steps to reproduce:
get a copper+ tier bundle (let's call this bundle 1) and fill it with items
get a second copper+ tier bundle (let's call this bundle 2) and place bundle 1 inside of bundle 2
fill the remaining space in bundle 2 with items
you can repeat the last two steps infinitely for infinite space

to fix this, you can either blacklist tiered bundles from going into each other, or use vanilla calculations for bundle weights

Thanks for reporting so detailed.

Is fixed in version 1.0.3

This issue was caused, because i checked only for the vanilla bundle on insert and not for the tiered bundles.