Greetings, It sounds like there is something loose, and moving the lid changes the linkage to it. You will have to begin checking everywhere on the piano to find the loose hingepin, screw, paperclip on soundboard, etc. Good luck,
Ed Foote RPT
http://www.uk-piano.org/edfoote/index.html Well-tempered CD's at Gasparo.com. GSCD #332, 'Beethoven In the Temperaments' GSCD #344 . 'Six Degrees of Tonality' Caution, these CD's contain pure intervals and extensive liner notes!