Issue with switching to ETH testnets

Bug Description
Issues when switching to ETH testnets in metamask on swap page.

Steps to Reproduce

1. Connect metamask to web-ui.
2. Switch networks to an ETH testnet.
3. The screen goes white. (with Kovan, the Kovan logo is shown next to wallet ETH balance in $ briefly, a few seconds max, and the screen goes white).
4. Can only be fixed by switching to either any smartchain (Fantom, BSC, HT etc) or ETH mainnet and refreshing the page. If refreshing the page with Kovan the page comes back for a second then goes white again.

Expected Behavior
For the 'Wrong Network' error to appear, or for the testnet name to appear to the left of the balance and stay there without the screen going white.

Additional Context
Brave v1.26.74 for macOS 11.4, with MetaMask 9.8.4