Daytrading buying power inconsistency "Insufficient day trading buying power"

I’m using alpaca-py. I call

client.get_account()

and see a value for

daytrading_buying_power and a
margin multiplier=4.

Then submit a market buy order and I get a code

40310000 “insufficient day trading buying power”

along with a value for daytrading_buying_power that is exactly the original value divided by 4.

What gives? What am I not understanding here? Want to understand.

On a more practical note, which attribute of alpaca.trading.models.TradeAccount should I use to get my actual buying power, since daytrading_buying_power doesn’t seem to be it. If I query for buying power, then only use 90% of what’s available, my expectation is I should not be getting rejected orders outside of very rare special cases.

Thanks.