Maybe when you put back the balance you overbanked-it by mistake - sorry if it is a stupid idea, I just want to help. Also check that the pallet engages the anker wheel properly (and lets it go also). Also check the balance wheel staff for proper vertical motion, check the antishock jewels to be centered.
Ah - the 1761 is either a calibre number, a serial number or a patent number - but it's not a date! The Mikrolisc site shows Lancyl as being registered in Langendorf in 1929:
Uhren, Uhrenteile; Langendorf, Schweiz; 1872/73 gegründet; registriert am 5.6.1929
So, your watch looks very 1950s to me...