The reflexes may inhibit, the childs development may be on course.

However - severe trauma - such as head trauma, severe and distressing illness and physical/emotional trauma can stimulate the reflexes to reactivate.

There may be trauma to, or ongoing inflammation in the cerebral cortex which inhibits its function. When the cerebral cortex is unable to function, the midbrains activity will heighten.

Galea, Olivia A., et al. “Sensorimotor and Physiological Indicators of Impairment in Mild Traumatic Brain Injury: A Meta-Analysis.” Neurorehabilitation and Neural Repair, vol. 32, no. 2, 2018, pp. 115–128., doi:10.1177/1545968318760728.

Taiello, A.C, Spartaro, R. et al. "The Primitive Palmomental Reflex in Amyotrophic Lateral Sclerosis", European Neurology 79(3-4):187-191, doi: 10.1159/000487993

It's important to note that we may not be just working with birth trauma and the first few months of life. There may be other reasons for inhibited reflex signs.

Sudden bedwetting, regression in behaviour, later diagnosed ADHD, sensory sensitivity that develops at a later age - are all signs.