I’m not sure what the source of the problem is. When I call the method signAndSubmitTransaction, everything works fine. However, when I try calling the methods getUnsignedTx and subsequently signTxx (like so):

      let tx = new TransactionService()
      const unsignedTx = await tx.getUnsignedTx('tx-endpoint', txPayload)
      console.log('unsignedTx:', unsignedTx);
      const signedTx = await tx.signTxx(unsignedTx)
      console.log('signedTx:', signedTx);

I get the error message: signTx: memory access out of bounds

Excerpt of the definition of TransactionService:

class TransactionService {
 ...
  
    async getUnsignedTx(endpoint: string, payload: any): Promise<any> {
      return this.postRequest(endpoint, payload)
    }

    async signAndSubmitTransaction(endpoint: string, payload: any): Promise<any> {
      const data: UnsignedTxResponse = await this.getUnsignedTx(endpoint, payload)
      const signedTx: string = await this.signTxx(data.urspTxBodyHex)
      console.log("Data: ", JSON.stringify(data))
      return this.submitTransaction(data.urspTxBodyHex, signedTx);
    }
  
    async signTxx(unsignedTx: string): Promise<any> {
      const ap = await window.cardano[this.walletName].enable()
      const signedTx = await ap.signTx(unsignedTx, true);
      console.log("SignedTx: ", JSON.stringify(signedTx))
      return signedTx
    }

    async submitTransaction(unsignedTx: string, signedTx: string): Promise<any> {
      return this.postRequest("tx/add-wit-and-submit", {
        awasTxUnsigned: unsignedTx,
        awasTxWit: signedTx
      });
    }
  
 ...
}

Web browser in use: Brave