My lever when pushed down (off) would bounce back and not release all the pressure. Turned out the flathead screw on the outside of the cam/lever was loose.

WS

Everything Ian has advised is correct but you may very well have two problems. The lever moves through a ninety degree angle from all off to all on. A TYPICAL value for the clearance between the lever's cam and the switch when the lever is down is ~ 0.048" = ~ 1.2 mm.

When you lift the lever to brew, it should stay in that position. A diagram from you might be helpful because it is hard to interpret "moves slightly down". As you say the machine is under warranty, here's hoping that the dealer you made the purchase from is in Moscow - I'd make a phone call.

erics wrote:A diagram from you might be helpful because it is hard to interpret "moves slightly down".

The diagram of the E61 parts in the brew position may be helpful:


From Is there a purpose for the E61 middle brew lever position?

When the lever is in the brew position, allowing water to enter the chamber, the leading lobe of the cam shown above is just past the stem that lifts the upper valve. That is, the cam/spring-loaded stem naturally act as a detent. It should not take much resistance to hold the lever in the upper detent position, since it's already held fairly snug in its travel by the sealing O-rings for the cam shaft connected to the lever itself.

Ron didn't mention the age of this machine, but a worn upper stem (#16), worn cam (#6), or weakening upper valve closure spring (#18) could result in less staying power for the lever. E61 Group Espresso Machine: Detailed Interior Schematics and the original E61 patent diagram will make these parts references clearer:


From The E61 Group - Truth and Lies

Coffeetime's How to Lubricate Your E61 Group includes some nice photos and notes a common sign of valve lifter wear is that the lever sometimes drops down on its own when pulling a shot.