Hydrometer in Wine Thief Tube

I took a hydrometer reading inside a wine thief tube yesterday. It was the OG for an all-grain hefeweizen. It read pretty low (1.03). I was in a hurry, so did not take another reading.
Anyone experience lower readings in narrower containers? I couldn’t imagine anything had gone wrong in the brew session.

As long as the hydrometer is free floating there should not be any issues.

Agreed. I take readings in my wine thief all the time.

About the only problem I have encountered is the exact opposite - if too much foam from Star San is in thr thief or too much CO2 in the solution, you get a higher reading until you de-gas it. That can happen in any container, of course, but can be particularly evident in the relatively tight space of a tube.

I doubt that it would give a falsely low reading unless it somehow is hanging up on the side of the tube for some reason when it gets dropped in there.

Calibration is always a factor. I have heard of wildly varying results from some hydrometers, but never tested any side by side.

I’m pretty confident in the reading, though everything was foamed up from aerating (which for me is dumping between 2 buckets several times.)

This was my first all grain (except for a previous BIAB). I did not open up the mash tun after the initial dough-in and stirring, so maybe I should have stirred it a few times?

I also had someone suggest that I may have drained the wort too quickly, leaving behind some of the sugars. I batch sparged, so I thought this wouldn’t matter. Draining first and second runnings each took just 5 or 7 minutes, with the valve about 2/3 open. Could that be the cause of the low OG?

Anyway, the bucket was foaming like crazy up through the airlock this morning. I rigged up a blow-off tube. I snatched a sample and the hydrometer read closer to 1.02 today.

No, that won’t cause a lower OG. I thought draining slower would help, so I tried it, and it made no difference.