this string will not work and breaks and resends the hello message twice
/tellraw @p ["",{"text":"breaks","color":"yellow","clickEvent":{"action":"run_command","value":"/tell @p hello"}},{"text":"","color":"yellow","clickEvent":{"action":"run_command","value":"/fill 170 60 632 170 60 632 minecraft:redstone_block"}}]

but changing it to this fixes it even though no error ever appears for the one previous.

/tellraw @p ["",{"text":"","color":"yellow","clickEvent":{"action":"run_command","value":"/tell @p hello"}},{"text":"works","color":"yellow","clickEvent":{"action":"run_command","value":"/fill 170 60 632 170 60 632 minecraft:redstone_block"}}]