Edit : Just saw yours is timber? I think my comments on SBCs/vinyl below doesn't apply, but try finding out if there are any other layers between your timber and cement floor.

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Not only the cement not done well, it's the cement cracked below the SBC/vinyl piece. My reno contractor lied to us that it was the SBC bad, the SBC supplier came to assess it and corectly identify it as buckling (cracked) cement layer due to bad workmanship. Contractor kept insisting SBC bad, but then said will put extra padding when changing the 'bad' SBC pieces/panels - meaning he knew it was uneven flooring due to cracked cement.

We observed the rectification process, and confirmed it was cracked cement causing uneven surface which the SBC then sinks into. This happened almost immediately after renovation completed (within 1 month).
Some of these panels have a thin layer of sponge between SBCs & and floor to absorb impact, so injecting cement won't really solve the issue, since the cement will be on the sponge and will also crack. Maybe inject silicone?