My estimate for when the 1st ep of 1KR was filmed is around July 16th - 18th. Jsng's hair was long on the 15th when they returned from B5T then it was cut short sometime between then and tbe cb press-con on the 19th. Bim's hair was fading at B5T and with the amount he sweated, you can see in the return airport photos that it had faded even more than it was at B5T. The other telling sign is L1x's roots. His hair and roots were touched up for the cb on the 19th, but at B5T he had slightly over grown roots just like in the 1KR teaser. So it was most likely filmed around July 16th - 18th.