Stargi pulled the rug. According to @HRitzdorf, "The admin upgraded to a malicious implementation. Example upgrade TX: https://polygonscan.com/tx/0xda8d237fecd19889e5eece67308711c6aff422b6465e832fdecee71e402f1fe4
Then the admin used the malicious implementation to steal all staked funds. The malicious implementation can be found here: "