Geneticist Kevin McKernan explains:

https://drtrozzi.org/2023/12/08/ribosomal-frameshifting/

Just Published Research Revealing This: N1-methylpseudouridylation of mRNA causes +1 ribosomal frameshifting.

By Thomas E. Mulroney, Tuija Pöyry, Juan Carlos Yam-Puc, Maria Rust, Robert F. Harvey, Lajos Kalmar, Emily Horner, Lucy Booth, Alexander P. Ferreira, Mark Stoneley, Ritwick Sawarkar, Alexander J. Mentzer, Kathryn S. Lilley, C. Mark Smales, Tobias von der Haar, Lance Turtle, Susanna Dunachie, Paul Klenerman, James E. D. Thaventhiran & Anne E. Willis