Transaction problems with ERC20 tokens may arise when the chosen fee to do transactions is set too low.
This usually happens when you add a custom ERC20 token for the first time. You most likely chose 75000 as the fee because that's the amount Metal Vault suggests. And that amount will work for most ERC20 tokens.
However, some tokens require a higher fee for transactions to work properly. Follow the instructions below to increase the fee amount. This quick fix will work in most cases.
Note: if token transactions worked without a problem before, there's no need to follow these steps. Open a support ticket instead.
Step 1: Remove The Linked Custom Token From Your Ethereum Wallet
Go to the "Tokens" page of your Ethereum wallet and click on the trash bin icon to remove the token. Don't worry, your tokens will still be in your Ethereum wallet.
Step 2: Add The Custom Again And Increase The Fee
Simply add the token again with the required token data. This time, increase the fee with 75000 increments. Thus try 150000 as the fee amount. If 150000 doesn't work try 225000. If it doesn't work with 300000, it's most likely another transaction issue.
Open a support ticket if this quick fix doesn't solve the transaction issues.