One of the eligibility requirements for sponsoring a family member is valid PR status. And, indeed, that is the first part of the family class PR visa application process: IRCC assesses the eligibility of the sponsor. Obviously, this may trigger inquiry into the PR's compliance with the PR Residency Obligation. If the sponsoring PR is not in compliance with the RO, this can lead to suspending processing the family class visa application pending the outcome of such an inquiry, and then lead to a formal Residency Determination. If the outcome of the latter is a conclusion the PR is NOT in compliance with the RO, a 44(1) Report for inadmissibility maybe issued, and if a Minister's Delegate determines that Report is valid in law, a Departure Order (or Removal Order) will be issued UNLESS there are sufficient H&C reasons for allowing the PR to keep PR status.
This does NOT always happen. We see mixed reports. A bit like driving under the influence, sometimes the drunk makes it home, sometimes the cops get him. (Except, to be clear, failing to comply with the RO is NOT wrong, let alone a crime; compliance is simply a requirement for keeping PR status and for exercising the benefits and rights of a PR.)
The process I describe above is discussed, with lots of citations and links to official and authoritative sources, in many topics here. I do not have time to revisit and repeat all that information.
But, to be clear: YES, a PR who is not in compliance with the PR RO MIGHT trigger proceedings to terminate her or his PR status by making a family class sponsorship application. Because the sponsorship application has triggered a review of the PR's compliance with the RO.
Sometimes it does not happen. So the forum sees reports of PRs who were in breach when they made a sponsorship application and things went OK. Maybe it has to do with how much (or rather how little) in breach of the RO the PR is. Or other circumstances.
But make no mistake, the PR who is not in compliance with the RO is RISKING losing PR status if he or she makes a sponsorship application.
The overwhelming conventional wisdom is that a PR who has been allowed back into Canada despite being in breach of the RO should avoid ALL transactions with IRCC or CBSA UNTIL the PR has stayed long enough to be in compliance with the RO. That means staying in Canada and not making any applications to IRCC, such as applications for a new PR card or to sponsor a family class visa application.
Some Particular Details:
"Specially if the PR is still valid for up to 5 years from date of issue. "
Does NOT work like that. The PR Residency Obligation is ongoing and continuous. A PR can be Reported and lose PR status even if a brand new PR card has been issued, if the PR is in breach of the PR RO.
For example, if the so-called "soft-landing" PR leaves Canada soon after landing and remains abroad for three years plus a day, that PR is then in breach of the RO and at risk for losing PR status EVEN though his PR card is still valid for almost two more years. That is, if a PR is abroad for more than 1096 days during the first five years, that is a breach, the PR is subject to losing PR status as of the day he has been abroad more than 1096 days. Dates on the PR card are NOT relevant.
There are many cases in which PRs are issued a new PR card and rather soon thereafter Reported, losing their PR status.