If LinnStrument's touch surface gets dirty, it's easy to clean.
For removing small amounts of dust between the pads, a small hand-held vacuum cleaner works well. Or for deeper cleaning between the pads, use a toothbrush with a little soapy water on it, but be careful not to let water seep into the edges under the metal plate.
For the most thorough cleaning, remove the top panel and the silicone playing surface, then wash it with soapy water, dry it, replace it and reassemble your LinnStrument. Here's a video showing how to remove and replace your top panel. Follow the example in this video, but also remove the rubber sheet, clean and then replace it before reassembling. When reattaching the top panel, take care to follow the video's instructions to not over-tighten or under-tighten the panel screws. Here's a good guideline:
Loosen the screw, then while pressing down with one hand on the top panel near the screw, turn the screwdriver clockwise with your other hand until the screw head is level with the top panel and you start to feel the increased resistance of the screw being fully seated in the hole. Then tighten an additional 1/4 turn only and no more. Note that the panel screws can be tightened within a very wide range and still work fine; there is only a problem if a screw is very tight or loose.
Note that in addition to securing the top panel, the screws above and below the playing surface also press the electrical contacts of LinnStrument's touch sensor against the mating contacts of the circuit board below it. So if a panel screw is too loose, the nearby column(s) won't send MIDI messages in response to Y-axis (forward/backward) movements. To verify that all columns are working after tightening the screws, make Y-axis movements on one pad within each column, verifying that each column is sending Y-axis messages in response. If one column isn't doing that, the screw(s) above or below that column needs to be tightened a little. If your synth has no way to inspect the MIDI messages that LinnStrument sends, you can use a MIDI monitoring application like MIDI Monitor on mac or MIDI-OX on Windows.