Is this the new Beta RX 250f ?

Good question.  
I think what happened is the acorn nut will deform the impeller before seating the shaft.  Adding a washer between the nut and impeller let's you tighten properly. As the impeller deforms it has no free play on the shaft.
 OR Could have been faulty oil seal, bearings, or assembly.

Either way, at <10 hours I was getting coolant in the oil, which was fixed with a waterpump rebuild kit.
 

https://betausa.com/2027-250-rx-4T/

https://youtu.be/nGoXH1tu6yQ?si=9M8v1izf_cPeHl-h

Interesting that it has two injectors. The 2028 KTM 250f (and maybe 350?) is also supposed to get a 2nd injector.

The Beta 350/390/430/480/500 enduro/trail 4 strokes have been dual injector for a while.

The only Beta that isn't dual is the 450.

It’s interesting that getting a flat was considered the ideal yet no manufacturer is as flat as a Beta… I wonder why? Is their a downside to not have an up-side? 

I meant getting a flat seat // weirdly I can't edit the above post

Big complaint for the MX purists is also accounted for on the 2027 model Beta RX bikes...

No more "off road" translucent fuel tank!

Now black like everyone else so you can't see in it and overfill it regularly.

Red/black has always been color combo of the “standard” bikes and red/blue has been the upgraded factory/race edition bikes for both the trials and enduro bikes.  Makes me wonder if there’s going to be special editions coming later that will be red/blue? 

Yeah they caved to the moto guys who don’t know how good it is to be able to see your fuel level 😂

I had begun to like the look of the Beta’s.  The ultra flat seat took a bit to get used to, but it doesn’t bother me now.  However, the micro side plates on this bike suck…

Who is US Beta gonna get to ride this thing?

probably Austin Forkner