Help understanding appraisal

[Kris Lamb]

So I am selling my house. It was a brand new house built in 2019 even though they say 2018(probably the year they submitted for permits) but have all the paperwork to show 2019. 

I originally listed as a FBO at 290 but became overwhelmed with that and staging and moving. So hired a realtor. We pulled comps and showed 299 would be listing price a bit on the high side but that's what the comps showed. The lowest comp was 278 and highest 303 average comp 290 according to my realtors comp sheet. So we listed at 299 and got an offer the first day of 305. We went under contract since 6-1-21 and the appraiser just came Tuesday 6-21-21 . We close on 7-2-21 . The buyers are using a VA loan like I did when I bought it in 2019. The appraisal called our realtors and told them it's appraisal is 284 and had 48hrs to show her better comps. I have been searching and pulling more comps from my neighborhood the highest comp sold in the last 90 days newest sale 50 sqft bigger was 320 and the newest lowest 50 sqft was 308 all new builds all sold prior to us listing. The only two house I found in my neighborhood that were resale were 310 100sqft bigger to 296 50 sqft bigger from a year ago. I had gotten a full detailed report from a broker that uses homecanary and the comps on it too and it showed 298 , it showed 289 on the lower and 310 on the higher end. We all feel the appraiser is low balling the house and missed newer comps. The buyers are willing to dispute it. I even provided paperwork from my refinance in 2020 showing the VA said it's worth 298 (my realtor said it never got submitted to the VA / even my current lender says my house is 298 and appraisal value at refi closing was 298)( I did an virrr so an actual appraisal wasn't required just pulling comps type)

My question is why would an appraiser come to such a lower number then all the comps pulled and every report we pulled? 
Is it worth disputing since everything I read says VA appraisal won't change and is an uphill battle.
Should we just wait out tell the buyers back out then re list and not accept and VA loans since this appraisal will stick on it for 6months.
The house doesn’t need any repairs. Only things found in the inspection were really minor things that I have fixed for free since the buyers only asked the carpets be professional cleaned.  The address is 1021 NE 34th Terr, Moore, OK 73160 .