Is it permissible for someone who doubted their bowing (rukūʿ), then prostrated, to return to bowing after prostrating, and is their prayer valid?

If doubt persistently afflicts a worshipper daily during their prayer, then it is a whisper (waswasah), and they only need to perform the prostration of forgetfulness (sujud al-sahw), without being required to rectify what they doubted. However, if the doubt is rare, then they must perform what they doubted, and then prostrate for forgetfulness, based on the hadith of Abu Sa'id, which is agreed upon. Therefore, whoever returns to the bowing (ruku'), completes their prayer, and performs the prostration of forgetfulness, their prayer is valid. A unit of prayer (rak'ah) from which a pillar is omitted does not become invalid until one reaches its corresponding place in the next unit of prayer.