Invalid requests errors while importing logs

I have been using Matomo import_logs.py script to import my nginx logs into Matomo.
This has been working without issue for months and yesterday I saw very many errors saying “invalid request”

I have searched through the forums and have found no reason why this is happening. I have only been pointed to Diagnostics and Tracking Failures, but when I look it is empty, with no errors.

It seems that there is something with the way the file is processed.
Below is the error. It occurs for all lines in the access.log file.

2020-03-26 21:27:24,320: [INFO] The Matomo tracker identified 200 invalid requests on lines: 21580, 21585, 21586, 21594, 21598, 21599, 21600, 21601, 21602, 21603, 21610, 21614, 21615, 21616, 21624, 21633, 21634, 21635, 21636, 21642, 21643, 21656, 21657, 21658, 21659, 21667, 21671, 21672, 21673, 21674, 21676, 21688, 21689, 21690, 21691, 21692, 21693, 21694, 21695, 21696, 21708, 21709, 21710, 21711, 21712, 21713, 21714, 21715, 21716, 21718, 21720, 21723, 21735, 21737, 21739, 21741, 21743, 21745, 21747, 21749, 21752, 21754, 21763, 21768, 21769, 21770, 21771, 21783, 21784, 21785, 21786, 21788, 21790, 21792, 21794, 21796, 21798, 21800, 21802, 21804, 21806, 21808, 21810, 21812, 21814, 21816, 21818, 21820, 21822, 21824, 21826, 21828, 21830, 21832, 21834, 21836, 21837, 21839, 21842, 21843, 21851, 21853, 21855, 21857, 21861, 21862, 21863, 21864, 21866, 21868, 21870, 21872, 21874, 21884, 21893, 21900, 21901, 21902, 21903, 21904, 21905, 21907, 21908, 21910, 21922, 21923, 21924, 21925, 21926, 21928, 21930, 21932, 21933, 21935, 21937, 21939, 21941, 21943, 21945, 21947, 21949, 21957, 21961, 21963, 21971, 21975, 21976, 21977, 21987, 21992, 21993, 21994, 21995, 21996, 22008, 22009, 22010, 22018, 22022, 22023, 22024, 22025, 22026, 22029, 22037, 22039, 22043, 22044, 22045, 22046, 22048, 22050, 22052, 22053, 22055, 22057, 22059, 22061, 22063, 22065, 22067, 22069, 22077, 22079, 22081, 22085, 22087, 22098, 22099, 22103, 22118, 22119, 22120, 22121, 22123, 22126, 22128, 22129, 22131, 22134

Thanks in advance for your help.
Regards
Lawrence