Is it a linguistic error that "O My servants who have transgressed against themselves" in verse 53 of Surah Az-Zumar is attributed to the speaker (the Prophet) instead of Allah?

There is no problem with the verse; rather, the misconceptions arose from a lack of understanding of the Arabic language and its styles. Ibn Ashour explained that the discourse can be broken down into two new beginnings: "Say" is a new beginning to clarify what the Prophet, peace and blessings be upon him, is to convey, and "O My servants" is an initial new beginning from Allah's address to them. This means that Allah commands His Prophet to convey His address to His servants as an honor for them, for the addition of "My servants" to the first-person pronoun contains an honor. Fath al-Bayan mentioned that the verse contains beautiful meanings and explanations, including Allah's turning to His servants and calling out to them, and attributing them to Himself as an honor. This verse holds wonderful secrets and is the most hopeful verse in the Book of Allah because it contains the greatest glad tidings.