File src/manager/walletwidget.ui specifies font "Monospace" to use for showing passwords. However, in case there is a font called "Monospace" installed on the system, this will be used instead of the default/system fixed-width font. If the "Monospace" font is broken or rendered incorrectly, passwords cannot be read from within the wallet manager.

To fix this problem, set a fixed font in C++ code by invoking setFont(QFontDatabase::systemFont(QFontDatabase::FixedFont)) which uses the fixed-width font as configured by the user.