The former German president has/had a consulting contract with Gazprom, and refused to stop it after the invasion. There are large groups in government who received payments from russian sources. A state minister actively worked to circumvent US sanctions.

So unless someone from German intelligence goes on the record I'd be very reluctant to believe any of these anti-Ukraine claims leaked to the press.

There's an interesting book called "BND: Bedingt Dienstbereit" which talks about German intelligence headquarters in Munich. The eastern German spies from the Stasi had their offices right across the street and they used that location to train new spies.

At some point BND learned that the Stasi was actively monitoring their offices, but they could never figure out where the Stasi was located in Munich. The BND always suspected a Turkish national who rant he vegetable shop at the ground floor of their building to be a foreign spy, but never noticed the Stasi offices used for training purposes right across the street.

So while I'm confident German intelligence has improved from those days it shows that the variance in skill level is quite high.