[Bug]: BNB swaps in legacy flow return error when fetching quotes

[SteP-n-s]

Describe the bug

On the latest 7.51 RC build (2151) quotes are not returned consistently when origin asset is BEP20.

Expected behavior

To receive quotes consistently.

Screenshots/Recordings

ScreenRecording_07-17-2025.09-07-30_1.MP4

Steps to reproduce

1. Open swaps
2. Select USDT or another BEP20 asset
3. Tap swap button

Error messages or log output

Detection stage

In production (default)

Version

7.51.0 (2125)

Build type

None

Device

iPhone 13 Pro

Operating system

iOS

Additional context

No response

Severity

No response

[infiniteflower]

Traced it down to this line in SwapsController, it seems to fail intermittently, think that points to the recurring RPC issues with the default BSC provider.

  const result = await contract.allowance(
        walletAddress,
        getSwapsContractAddress(network.chainId),
      );

[infiniteflower]

Closing as we believe this is an intermittent BSC RPC issue.

Migration to Infura for BSC is happening in #16824

[github-actions]

Hi @SteP-n-s,

This issue has been closed. Please complete this RCA form:
https://docs.google.com/forms/d/e/1FAIpQLSdnPbJISzFlR_aQD2uRpnMKSoGAopuTd_yeZK7J4Q5GzgbsOA/viewform?entry.340898780=17323&entry.1228565618=regression-RC-7.51.0&entry.1698032149=team-swaps-and-bridge