I'm using an Alpha Framework algo and backtesting. At some point in each backtest, I hit a string of Invalid orders (intermittently, using a variety of ETFs).  I'm attaching an example.  What I see is that at some point, instead of a valid price, I get a price of '$USD' on an order.  This generates a string of invalid market orders that are re-tried all day.  If I switch out the ETF with the invalid price, and re-run the test with other ETFs, eventually I hit the same problem with another ETF.