Hi,
I think of Maks as being quiet and lower power versions of the Iwakis.

The Mak5 is pretty close to a 70RLT and a Mak4 is pretty close to a 55RLT.
The Apr/02 fix was to relieve pressure on the seals so that the rotor can spin more freely. The original problem causes the motor to work hard and grind the seals even faster. I guess they were hoping that they can make the seals last longer by relieving the pressure. However, it does not fix the fact that seals always grind against each other in normal operation. Eventually, the seals with grind away and start to leak...as it is suppose to.
When you have time, do you think you could post a picture of your tank ?
- Victor.