There's a video on YT with the video description is below. Looks like it could be related to your issue. This is also a Sabre 450 bandsaw.
"When trying to mount an original Record Power 3/4" (19 mm) blade the tension system all the way up still wasn't enough the have enough tension on the blade. By contacting Record Power the factory adjustment was pointed out as the option to still have the blade properly mounted. In this video it is explained and demonstrated how this can be done.Bandsaw: Record Power Sabre 450Blade: Record Power 3/4" (19mm), 3 TPI, L=3885mm, t=0.8mm"
"When trying to mount an original Record Power 3/4" (19 mm) blade the tension system all the way up still wasn't enough the have enough tension on the blade. By contacting Record Power the factory adjustment was pointed out as the option to still have the blade properly mounted. In this video it is explained and demonstrated how this can be done.Bandsaw: Record Power Sabre 450Blade: Record Power 3/4" (19mm), 3 TPI, L=3885mm, t=0.8mm"