why we cannot have two reimer tiemann substitutions on the same phenol as CHO- group is electron withdrawing it wont disturb electron concentration at its meta which is phenol's ortho- product
There are some literature evidence that shows to have two Reimer–Tiemann substitutions on same phenol ring could be possible. For example, salicilic acid is a Reimer–Tiemann product from phenol and carbon tetrachloride. Yet, it had undergone another Reimer–Tiemann reaction to give 5-formyl-2-hydroxybenzoic acid with $17\%$ yield (para-substitution) but no 3-formyl-2-hydroxybenzoic acid (ortho-substitution) when chloroform was replaced by trichloroacetic acid (J. Chem. Soc., 1933, 496-500).
For more examples: Read, Chem. Rev., 1960, 60(2), 169–184.