McSpadden Friction peg replacement
Instruments- discuss specific features, luthiers, instrument problems & questions
I've always found slipping wooden pegs to be nicely cured with a minor treatment of Peg Drops liquid. You can't lose anything by trying it out before opting to completely change to geared pegs.
Wood pegs tend to slip more in the Winter dry indoor weather. The Peg Drops liquid is made with rosin and provides a nice even very thin film of 'grip'- makes tuning/moving them smoother, and pegs then will hold. You need to unwind the string and remove each peg in turn, put 2 or 3 (no more than that!) drops and evenly turn the peg in place to spread where the peg touches against the wood. Then restring the string, tune up with a little less tension than usual, and let the drops 'cure' overnight before tuning up to normal.

What a terrific photo, Sam!