api: Error: createType(Text):: Text:: Decoded input doesn't match input

Hi, I call my smart contract functions and they return correctly but when I call one specific function in polkadot.js, this error happens:

Error: createType(Text):: Text:: Decoded input doesn't match input, received 0x2070726f7669646572 (9 bytes), created 0x242070726f7669646572 (10 bytes)
    at createTypeUnsafe (node_modules/@polkadot/types/create/createType.cjs:58:11)
    at formatData (node_modules/@polkadot/api-contract/util.cjs:20:39)
    at MapSubscriber.project (node_modules/@polkadot/api-contract/base/Contract.cjs:162:81)
    at MapSubscriber._next (node_modules/rxjs/internal/operators/map.js:49:35)
    at MapSubscriber.Subscriber.next (node_modules/rxjs/internal/Subscriber.js:66:18)
    at RefCountSubscriber.Subscriber._next (node_modules/rxjs/internal/Subscriber.js:89:26)
    at RefCountSubscriber.Subscriber.next (node_modules/rxjs/internal/Subscriber.js:66:18)
    at ReplaySubject.Subject.next (node_modules/rxjs/internal/Subject.js:60:25)
    at ReplaySubject.nextInfiniteTimeWindow (node_modules/rxjs/internal/ReplaySubject.js:50:31)
    at ConnectableSubscriber.Subscriber._next (node_modules/rxjs/internal/Subscriber.js:89:26)
    at ConnectableSubscriber.Subscriber.next (node_modules/rxjs/internal/Subscriber.js:66:18)
    at /Users/project/node_modules/@polkadot/rpc-core/index.cjs:262:20
    at processTicksAndRejections (internal/process/task_queues.js:93:5)

The function in ink! contract

 pub fn get_username(&self) -> String {
            let caller: AccountId = self.env().caller();
            match self.address_to_username.get(&caller) {
                Some(username) => username.clone(),
                None => panic!("this address has not a valid associated username!"),
            }
}

I use these versions:

 "@polkadot/api": "^4.9.2",
 "@polkadot/api-contract": "^4.9.2",

Thanks for helping:)