If you summon Falling Sand Inside the block (Summoning a log falling sand inside a log block) will cause an invisible glitchy barrier which you cannot pass through. The only way to destroy it is with /setblock or /fill or by placing another block inside it.
Duplicate of MC-72248. If you have not, please use the search function in the future to check whether your bug already has been reported. More than 50% of all bugs ever reported had to be closed as duplicate.