Yes I have a 2015 Silverado and have the same issue , noticed it in middle of July 2018, only drivers side front. took it to chevy, 1st time claimed it was clogged drain, problem still existed, switched dealers first time they claimed could not find anything, brought back when floor was wet-- they said it was the fin antenna - replaced --- problem still there, back in Sept this time they said they sealed areas in firewall etc-- problem still there - back in Oct they sent to auto body - took whole interior out found loose rear vent --- (they had truck 1 month) other times about week at a time
then in beginning dec looks like it came back again.. they had it whole month dec - supposedly had GM eng look at it and end of month said they could not find anything... seems to have been good most of 2019 but stopped looking fast forward to Jan 2020 issue is back..... and Chevy now saws not there issue out of warrenty etc...…….
