Does anyone else have problems with Bb1?

That should not be a particularly difficult pitch to produce assuming your flute is in working order. Has it been to see a tech recently?

It's brand new YFL-381.

If it's brand new, it may well need some setup from a tech. Most flutes don't come out of the box fully set up, and yours may well fall into this category. I would suggest asking a tech to look it over (which should not cost anything unless you agree to engage them for actual work), and see if they think it needs a bit of adjustment here and there.

Bb should be just as easy as B or A. The flute will be out of adjustment.

The standard B fingering includes the 'f' key. Instead of pressing that down, press the tiny "aux Bb" lever just above it. Alternatively, use the right hand to press down not F and Eb keys, but the Bb key (just above the A key).

If that makes Bb work well, then your problem is the linkage from the F key to the Bb key.

I think you were right. It did make a differance and I place a piece of masking tape under the linkage connecting the 2 keys and it helped a lot. The Bb key had a slight gap when Bb was fingered and the tape closes key all the way now. Thanks for tip.