Zodiac Vortex JD clean 4x4 - Cleaner does not climb pool sides

Vortex™ range
The cleaner does not or no longer climbs the pool sides
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Clean the filter
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Check whether the brushes turn at the bottom of
the sides
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Check the water quality, the sides are perhaps
slippy
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Check for brush wear
Start the cleaner
Troubleshooting assistance