The L-subshell internal conversion electron ratios of some hindered electric dipole transitions in the odd-mass nuclei 171Tm, 175Lu and 177 Hf have been measured by means of a high resolution ironfree double focusing beta-ray spectrometer. Large anomalies have been observed in the conversion process. The anomalies are interpreted as an experimental evidence for the presence of dynamic effects. The internal conversion penetration parameters have been determined. The results obtained are discussed in terms of theoretical predictions.