The event that allowed Lapras shiny began on April 18 and finally ended on the 22nd of the same month, or at least that was what Niantic expected. When the event was finished, users discovered that there was a bug that allowed 5 extra incursion passes , a bug they took advantage of before reporting it.
The bug fix did not remove the additional raid passes achieved
Once the event was over, Lapras reappeared as level 4 raid chief , prompting players to take eternal walks to visit different gyms in his city, thus achieving five extra raid passes. With these five passes you could get this pokémon with perfect stats and in its variacolor aspect, better known as “shiny”.
Social networks were the first to echo this bug that users were taking advantage of. The bug was that the player, by the mere fact of approaching a Pokémon GO gym and spinning the disc, received additional raid passes. Thus, those fortunate ones who were quickest had the possibility of gaining additional raid passes.