What is a common mistake in قَدْ أَفْلَحَ?

Rules of Hamzah — Taḥqīq, Tashīl, Ibdāl and Hamzat al-Waṣl

• Keeping dāl sākin clear
• Dropping hamzah and moving its vowel to dāl
• Recognizing hamzah after dāl
• Reading both clearly