Nine times out of ten the cause is sand compacted in the bottom channel and worn rollers. Less often it is the guide itself, bent or shifted. The first takes ten minutes to fix; the second needs a technician.
01THE CHANNEL FIRST, EVERYTHING ELSE AFTER
Run a vacuum with a narrow nozzle along the whole track, not only where it stuck. Then wipe it with a damp cloth and let it dry.
02DO NOT OIL THE TRACK
Oil attracts sand, and a week later it is worse than it was.
03THE ROLLER MUST TURN FREELY
Spin it with a finger. If it is seized or grinding, there is sand inside. A roller is a consumable and costs little.
04WHAT TO DO YOURSELF AND WHAT NOT TO
- Yourself: clean the channel, wash the rollers, tighten visible fixings
- Not yourself: straightening the track
- Not yourself: opening a roll-up cassette — the spring inside is under tension
- Still jumping off after cleaning: it is not the sand
Check the channel first
Lift the screen off the rail if it comes off, and look into the channel. In Dubai fine sand gets in there and compacts into a dense layer that the rollers cannot ride over, so they start skipping.
Vacuum the channel with a narrow nozzle along its whole length, not only where the screen stuck. Then wipe it with a damp cloth and let it dry.
Do not oil the channel. Oil attracts sand, and within a week it will be worse than before.
Then look at the rollers
A roller is the small wheel at the bottom of the frame. Spin it with a finger: it should turn freely and without grinding.
If a roller is seized or grinding, there is sand in the bearing. Sometimes washing it out works; more often the roller gets replaced. It is a consumable and it is inexpensive.
If a roller is broken or its axle has worked loose, the screen will keep jumping however often you clean the channel.
When the guide itself is the problem
Sight along the rail with your eye at one end. It should be straight.
If the guide is bent in one place, it can sometimes be eased back carefully. If it is deformed along its whole length it cannot be trued, and it gets repositioned or replaced.
The second case: the guide has pulled away from the opening and its fixings have loosened. The screen then runs skewed and the rollers carry uneven load. The fixings get moved, sometimes to a different point.
Nine times out of ten it is compacted sand in the bottom channel and worn rollers, not a failure of the mechanism.
What you can do yourself and what you cannot
Yourself: clean the channel, wash the rollers, tighten visible fixings, put the screen back on the rail.
Not yourself: replacing rollers on a construction you have never taken apart, straightening a guide, opening a roll-up cassette. The spring inside a cassette is under tension and reassembling it truly is difficult without a bench.
If the screen still jumps after cleaning, sand is not the problem and you will need a technician.
