Hygena APL8224/1 – water remains after cycle ended

Hi there,
Can anyone help me please? I have a Hygena dishwasher Model APL8224/1 – (Type 8.P2.2144211). After they cycle is finished there is water remaining in the bottom. This has occurred suddenly – i.e. after one cycle there was no water, after the next there was.
I have checked the filter that I can find by removing the front half of the large filter at the bottom. This is not blocked. I removed this filter and cleaned up a small rubber flap. I could feel another similar flap by poking my finger down the exposed pipeway. This appeared to be “flapping” freely.
I retested the rinse part of the cycle and again there was a build up of water. Most of the time the noises coming from the machine sound normal, though at one point it sounded as though a motor was having some trouble.
I am wondering if there is any point in checking further for a blockage (is there another filter further along?), or is it most likely to be a pump motor of some sort. During the test cycle I could hear a lot of what seemed to be normal pumping noises as well as the noisier non-normal ones.
If I am looking at a new motor, is this a component I can install myself, or am I needing professional help?
Many thanks
Phil