There are several aspects to the problem. One are the referenced coolant leaks in the wing pods of the DASS self-protection suite, where the maker of spares changed ownership which seems to have lead to non-availability without the Luftwaffe noticing (I take it this refers to the recent forming of Leonardo, who are now listed as the maker of DASS). This means only eight to ten Eurofighters are currently rated fully combat-ready. I'd be interested to know how this affects other users; knowing the anal German way, they probably just sourced alternate parts without as much fuss. I recall the Brits took a very pragmatic approach to a propeller problem which severely impacted the Luftwaffe's A400M fleet.
The "only four aircraft" bit relates to the fact that there appear less than 20 servicable AIM-120 left of the 80-100 procured from 1996. Some were fired in tests and exercises of course, but it seems that as part of the penny-pinching in recent years, the rest was not maintained properly in expectation of them being replaced by Meteor soon anyway - which has however been delayed. Since warload is four AMRAAM per aircraft, you can only fully equip four of them thusly (though of course you could put two each plus IRIS-T on all otherwise combat-ready aircraft).
Overall, the Bundeswehr's airfleet remains in a sorry state. There is a report today that last year, 19 of 129 Tiger pilots had their license lapse because there weren't enough flyable helicopters to get their minimum flight hours (the Bundeswehr has recently taken the unusual way of having them fly on civilian helicopters by agreement with the ADAC, the German motorist club which runs Germany's biggest fleet of MEDEVAC choppers). Another recent report was that seven Eurofighter pilots have quit the service this year alone, which got some publicity when a female jock who had gotten exposure by winning selection for one of two slots by a private initiative to get a female German astronaut to the ISS joined them (she also gave up that slot, and the initiative hasn't collected the necessary money for the training by far with the deadline approaching, so everything is not roses on the private aerospace side either).
This has also been linked to the lack of flyable fighters, though the problems run deeper. For some years now, Luftwaffe pilots have complained that their original special contracts for serving in a flying capacity to 41 years of age, then leaving with a 55 percent pension are being turned into standard lifer contracts and the Luftwaffe puts them wherever it needs them (more than in a marginally available aircraft fleet anyway), including driving UAVs and unglamorous desk jobs. I can certainly understand them being pissed about the service unilaterally going back on agreements made, and quitting in return as is the right of any lifer at any time (though without the pension benefits), even if the often-expressed attitude of "I joined to be a pilot first, not a soldier" annoys me; if you just wanted to be a pilot, you could have joined Lufthansa, but apparently you wanted the thrill of flying a fighter jet, the purpose of which is, well, military.
It is of course no accident that all these reports are coming out at this precise time; as I noted over in another thread, Defense Minister Ursula von der Leyen is trying to wrangle out a total increase of twelve billion Euro for her budget this term rather than the 5.5 in the finance ministry's initial draft (of which three billion are really for pay raises recently agreed for all public services). She has threatened that otherwise one of several planned European cooperation projects like the joint German-Norwegian submarine project or procurement of six C-130J for a joint SF support squadron with France would have to be cancelled, putting extra foreign policy pressure on the dear coalition partner of the SPD.
She also took the unusual step of a joint note with Development Minister Gerd Müller in cabinet that they were only consenting to the budget draft in the expectation that it will be improved upon in subsequent deliberations (the new CDU/CSU-SPD coalition agreement mandates that both their budgets are to be increased in step, as Germany currently doesn't fulfill the ODA target of 0.7 percent of its GDP for developmental aid at 0.5 percent either). So media coverage should be seen as part of the fight over money, though of course that doesn't mean the problems aren't real.