Assertion failure on `get_cstrs` of simple abstract domain

[rmonat]

Considering the program below:

open Vpl__UserInterface.UncertifiedZ

let x = Vpl.Var.fromInt 1 and y = Vpl.Var.fromInt 2


let _l1 =
  let r1 = assign [(x, Vpl.Domains.InterfaceZ.Term.Var y)] top in
  get_cstrs r1


let _l2 =
  let r2 = assign [(y, Vpl.Domains.InterfaceZ.Term.Var x)] top in
  get_cstrs r2

And compiling with ocamlfind ocamlopt -o vpl_test -linkpkg -package vpl-core vpl_test.ml, I currently get an error on the second get_cstrs:

$ OCAMLRUNPARAM=b ./vpl_test 
Fatal error: exception File "ocaml/datatypes/Vector.ml", line 263, characters 2-8: Assertion failed
Raised at Vpl__Vector.Make.rename in file "ocaml/datatypes/Vector.ml", line 263, characters 2-39
Called from Stdlib__List.fold_left in file "list.ml", line 121, characters 24-34
Called from Vpl__Cstr.Make.rename_f in file "ocaml/datatypes/Cstr.ml", line 233, characters 23-50
Called from Stdlib__List.map in file "list.ml", line 92, characters 20-23
Called from Vpl__TrackedDomain.Make.Track.unary_other in file "ocaml/interface/TrackedDomain.ml", line 40, characters 22-26
Called from Vpl_test._l2 in file "vpl_test.ml", line 13, characters 2-14

Would there be a way to fix this issue? I'm using OCaml 4.14.1 with VPL 0.5 installed through opam.