simplify removes metadata on certain terms created by substitution

[hexaeder]

MWE

import Pkg; Pkg.activate(temp=true); Pkg.add("Symbolics")
using Symbolics

@variables t a(t) b(t) c(t) d(t)
term1 = a - c - d |> Symbolics.unwrap
term2 = substitute(a - b, b=>c + d) |> Symbolics.unwrap

term1s = simplify(term1)
term2s = simplify(term2)

Symbolics.metadata.(Symbolics.get_variables(term1))
Symbolics.metadata.(Symbolics.get_variables(term2))
Symbolics.metadata.(Symbolics.get_variables(term1s))
Symbolics.metadata.(Symbolics.get_variables(term2s)) # all metadata gone!

The only difference between term1 and term2 i found is that term 1 creates a + operation with 3 arguments. Term 2 on the other hand is a + with two arguments, one of which is a + operation itself.

This might be related to JuliaSymbolics/SymbolicUtils.jl#434.

Sorry the ecosystem is moving to fast for me to follow closely, I am not sure whether this should go to Symbolics, SymbolicUtils or MetaTheory.

[hexaeder]

mwe works now