Learn Portuguese (Portugal): Eles implementam salvaguardas contra quaisquer falhas. - They implement safeguards against any failures.

The word qualquer is an old combination of qual (which) and quer (wants). In Portuguese, this word pluralizes internally: only the first half changes. Since words ending in -al change to -ais in the plural, qual becomes quais, while quer stays the same, resulting in quaisquer.

Because falhas is feminine, shouldn't quaisquer change to match its gender?

No, quaisquer only changes for number, never for gender. Just like its singular form qualquer, it is gender-neutral and can be used with both masculine and feminine nouns like the feminine word falhas.

What is the difference in meaning between saying contra quaisquer falhas and contra algumas falhas?

Using quaisquer translates to 'any failures' or 'any failures whatsoever', emphasizing that absolutely no failure is an exception. If you used algumas falhas, it would mean they only implement safeguards against 'some failures', which implies they are still vulnerable to others.

The word salvaguardas looks like a combination of two words. Is it pluralized normally?