In the SubversionSettings gridLayout verticalLayout QCheckBox kcfg_check_needslock, the whatsThis text ends as follows:

    But due this listings/updating on folders containing lot of items may get slow.
    So you should only switch on if you have repositories containing lot of such entries.

I propose changing the sentences to:

    But on folders containing lots of items this listing/updating may get slow.
    So you should only switch on if you have repositories containing many usages of the property.

I am aware that "But" and "So" as first words are awkward.
Could be further improved by using "However," and "Therefore," respectively:

    However, on folders containing lots of items this listing/updating may get slow.
    Therefore, you should only switch on if you have repositories containing many usages of the property.