All the keyboard has a degree of being loose... But the problem is harsh at the middle area...

is it fixable?

This test should be done with minimal strength, looks like you are pushing it a bit to me.
In either case, the fix is easy - rebushing keys is routine maintainance. Short term inexpensive fix is to turn the front pin slightly but I do not like to do that.

I agree with Gene about it looking like you are pressing it too hard. The cloth bushing the pin rides in has a little give to it. The numbers 5-10 thousandths of an inch come to mind for the amount of side to side play on the key with minimal force...this is about the thickness of 2-3 pieces of paper. Another quick test is to lightly push two adjacent keys towards each other using friction of your fingers from above (not pinching them like in the video) and then alternately press them down; they should not rub or touch and you should see some gap between them. If the oval shaped pins have already been turned in the past, then it looks like you would need to re-bush these...otherwise they don't look too bad from the pressure your putting on them.

The repair is a job for a skilled tech. But I believe it would be very helpful to get a copy of Authur Reblitz book on piano repair/rebuild. Not with the intention of doing it yourself but to have knowledge of just what is worn and how it will be corrected.

Does it affect your playing?

James

hi James. Thanks for the book. It does affect the playing, the keys at the middle are not "tight".

Made a new video... Are you guys sure a key rebushing will solve the problem?

fe2008 If you don't know how to replace key bushings or the piano is not worth spending too much time on I have found the best way is to first remove all the keys and replace one at a time adjusting the loose play with a key spacer tool. Push each key down to the bottom of the stroke and feel the looseness there not at the resting position. With the spacing tool rotate the front guide pin anticlockwise until there is only the slightest movement sideways. Doing it this way the sharps can also be ajusted properly. The only wild card is if the front bushings are badly moth damaged. Even then rotating the guide pin will work.
Robin Stevens ARPT
South Australia