Oki PT390 Manuel D'utilisation page 46

(10) If label paper is used, adhesive matter adhering to the cutter blade, thermal head,
paper transport, or paper holder may cause a cutting error, print error, or paper
transport error. Remove adhesive matter periodically (typically on a monthly
basis).
(11) If paper is left inserted in the printer for a long time, the paper may become
deformed and result in thin (faint) printed characters. Before starting printing in
such cases, feed the paper by 20 to 30 mm.
(12) If the type of paper used is other than the recommended ones, the print quality and
thermal head life are not guaranteed. In particular, if the type of thermal paper
contains Na+, K+, or Cl-, the thermal head life may be significantly shortened.
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