Error while pushing data

You're probably right to suspect a concurrency issue. Excel via the Graph API isn’t always great with handling multiple simultaneous write operations — especially when you’re hitting the same workbook or worksheet. It often processes requests sequentially, so if both pushes overlap in timing, one can get dropped or delayed without error.

You might want to try adding a slight delay between requests or batching the updates into a single payload if possible. Also, check if you're targeting the exact same usedRange — sometimes the API behaves weirdly if it's recalculating the range while you’re pushing data.