You repair one fault, then other starts creating issue, but when you fix this fault, then you find problem in other part.. i think there is something wrong in airframe !
Start it again from scratch
"Something wrong in airframe" is too vague. No airframe is perfect, it's always a compromise between many parameters. There are quite a few shortcomings we could ascribe to Tejas' airframe - for one thing, it is too draggy, when compared to fighters of similar size. For example the Gripen, which is slightly bigger, and running on the same engine, has superior aerodynamic characteristics. One could say therefore, that the Gripen has a better airframe.
But then, sometimes shortcomings are intentional - the F-35's airframe has inferior aerodynamic performance (maneuverability, agility) compared to the F-16, but that is more than offset by the F-35's "very low observability". It was a trade-off between the two, and the designers consciously chose stealth as a more important factor.
Anyway, there would be "something wrong in the airframe", only if the aircraft cannot stay airborne. If the airframe is shaped like a pyramid, it is not going to be capable of flight, ever. But of all the designs that can actually fly, you can't say there is something wrong with the airframe, unless you mean either that it cannot fly, or that it does not meet a certain flight characteristic that the designers were asked to meet. If the Tejas' ITR or STR or AoA or max speed is below what is needed, and it is not due to lack of thrust (engine), then one could say that the airframe has to be redesigned. But as far as we know from public info, there is nothing wrong in the way Tejas flies, and the test pilots have gone on record stating that it is a delight to fly, like the Mirage-2000 (which was the inspiration for the design).
The delays in the program have nothing to do with airframe design issues. The fact is that airframe is only the first step, there is so much more to make the aircraft not just a flying machine, but a warfighting machine. That is where India had zero experience (only a handful of countries do), and Indian engineers are having to plod the slow, laborious path towards completion.
The airframe is more than good - in the sense that 1)it can fly, and 2) it can be flown better and easier than one of IAF's favorite aircrafts, the M2K. But a modern fighter jet is a very complex machine, it not only has to fly, but it has to hunt, it has to kill, it has to avoid being hunted, avoid being killed, it has to communicate, it has to search, it has to...
The delays are to be expected, when a bunch of people with zero experience and foreknowledge embark upon such a difficult venture. It was foolish to think that ADA/HAL could design and operationalize a 21rst century fighter in the same timeline that Europeans or Americans could.