[en] The destabilization of the robust antiferromagnetic/charge order insulator (AFM/COI) phase in La_{1-x- y}Pr_yCa_xMnO₃ through La³⁺ substitution give rise to delicately balanced coexistence of ferromagnetic metallic (FMM) and antiferromagnetic insulating (AFMI) phases. The CO-disordered compound La_{1-x- y}Pr_yCa_xMnO₃ shows (i) intrinsic non-ergodicity and (ii) multiple magnetic transitions (iii) magnetic liquid phase and (iv) strain glass at low temperature. These are ultrasensitive to external thermal and electromagnetic variables. In thin films of this compound the above features pronounced and strain tuneable. The present study reports the evolution of the magnetic liquid phase and the soft strain glass as a function of the magnetic field (H) in La_{1-x- y}Pr_yCa_xMnO₃ (x≈0.40, y≈0.40) thin films. (author)