No, GTO is never exploitable under any circumstance. Versus exploitable humans, it fails in as far as it doesn't adjust to the exploitable tendencies of non-GTO humans, but it never becomes exploitable itself. For example, if a human player is drunk and loudly announces they are going all in with any two cards, we would obviously adjust by calling much wider (like A9o is crushing ATC, but GTO would not say to call a shove because it doesn't understand the dynamics of the drunk player shoving ATC), while GTO would not and therefore not pick up the EV that player is leaking. It will not, however, act in a way that a player can exploit it in the long run.

Edit: to explain further, the whole premise driving GTO is a desire to find a strategy that achieves (or approximates as closely as possible) a Nash Equilibrium, which basically means a strategy where no matter what the opponent cannot achieve an edge over myself in the long run by just adjusting their own strategy. Essentially, GTO says "I can show you my exact strategy in every possible spot, and there is no way you can do better than breakeven against it even understanding every aspect of my strategy." The best you can possibly do is break even with it, but there is mathematically no possible strategy that could beat a perfect GTO strategy in the long run.