The manager is liable for damage arising from their activity under the general damages rules of the Civil Code, meaning liability is tied to culpable conduct: if they demonstrably failed to do something that could reasonably be expected in the situation, this can create a basis for liability.
It is important to separate liability from decision making: the manager executes the resolutions of the general meeting, but the decision is made by the meeting itself. If a resolution later proves poor, that is not in itself the manager's liability, unless they gave misleading or incomplete information when preparing it.
Typical cases in practice are missed statutory deadlines, careless bookkeeping, regular unjustified neglect of fault reports, or breaching a contracting obligation. In such cases the community can claim damages, including through litigation.
Exemption is possible if the manager proves they acted as could reasonably be expected, which in practice means recording decisions, proposals and their reasoning in documented, retrievable form, as this is the only reliable evidence of diligent conduct in a later dispute.
This is exactly why professional liability insurance matters: a professional management company typically holds such cover, which provides for proven damage without the cost falling back on the owner community.
Merbo documents every decision process and holds professional liability insurance, so owners and the manager can work together within transparent, secure boundaries.