I always use bio powder and have a cold fill machine too. I stopped using liquids when I started getting dirty marks on my washing - apparently a build up of slimy stuff in the drum/rubber seal which is more common with liquids.
there is a chance that your machine contains a resident sludge of old powder and conditioner. This is very common if you do a lot of cool washes.
Put some old cotton towels in it (no soap or conditioner) and do a HOT MAX wash. If there is old sludge, this will tend to wash it out, and you will see the machine foaming up even though you added no powder or gel. Do it again. When it stops foaming, even on HOT, then you can be fairly condident that the old residue has mostly been washed away. Do this maintenance wash every few months.
BTW if you use a lot of bath oil or skin cream, or I suppose if you work in a chip shop or ice-cream factory. you may get a grease buildup in the machine, again a HOT MAX wash with old towels, but this time add Ariel powder which is quite strong.
i also only use a teeny tiny bit of gel... perhaps 1/8 - 1/6 of the recommended amount. (my clothes are always clean and you can smell the detergent too, i cant really imagine how strongly they would smell if i used the recommended amount!
If you are that worried use a small amount of super concentrate liquid and mix with water before putting in machine so its already a bit more liquidy?
Using liquids / gels & low temperature is notorius for making washing machines and the pipes etc really gunky and manky so best to use a biological powder, and hotter washes sometimes as well to minimise this.