Pages test has fluctuant failure

Pages test has fluctuant failure. It's failing from time to time with:

Use of uninitialized value of type Str in string context.
Methods .^name, .raku, .gist, or .say can be used to stringify it to something meaningful.
  in sub get_etalon_records at ./t/18-pages.t line 143
Use of uninitialized value $rnd_sample of type Str in string context.
Methods .^name, .raku, .gist, or .say can be used to stringify it to something meaningful.
  in block  at ./t/18-pages.t line 125
Use of uninitialized value $rnd_sample of type Str in string context.
Methods .^name, .raku, .gist, or .say can be used to stringify it to something meaningful.
  in block  at ./t/18-pages.t line 125
Use of uninitialized value $rnd_sample of type Str in string context.
Methods .^name, .raku, .gist, or .say can be used to stringify it to something meaningful.
  in block  at ./t/18-pages.t line 125
Use of uninitialized value $rnd_sample of type Str in string context.
Methods .^name, .raku, .gist, or .say can be used to stringify it to something meaningful.
  in block  at ./t/18-pages.t line 125
Type check failed for return value; expected Str but got Any (Any)
  in method encode_utf8 at /usr/share/perl6/site/sources/855EFC9327D3FE3339D98FF7DBC103BB78FDD639 (LZW::Revolunet) line 36
  in block  at ./t/18-pages.t line 106
  in block <unit> at ./t/18-pages.t line 97
    # You planned 27 tests, but ran 6