If you are getting Error 14 with every blank you try, the burner is probably dying, but to be sure you'd need to try different brands and types. That can be difficult today, since 9 out of 10 brands are really made by just two companies. Even the once-invincible Verbatim DataLife Plus 8x DVD-R and TY/JVC have developed compatibility issues the past few years.
Exactly which blank Verbatims are you using? The version sold most commonly in stores and on Amazon is rated for 16x speed and not actually made by Verbatim: the orange/purple packaging needs to have the word or symbol "AZO" on it somewhere, or the discs are just generic junk that doesn't work well in recorders. Verbatim recently began backing away from "Genuine AZO" at retail: most of the spindles I see in stores "look" like the old AZO packaging but aren't labeled AZO (and identify as Ritek or some such when loaded in a PC). Like every other brand, production of most "Verbatim" media is now subcontracted to lesser mfrs.
People don't like hearing this, but DVD recorders are beyond dead and buried as a viable consumer product. The last really good ones designed for North America were discontinued nearly ten years ago, and those were already buggy and picky about blanks to begin with (your Toshiba XS-35 being one of the most notorious, known for its truly craptastic picayune dvd burner). None of these machines were meant to survive more than four years at the outside. The fact that you have an XS-35 that was still functional until just recently is pretty amazing: their durability track record is dismal.
I love DVD/HDD recorders, and still use mine every day for both VHS conversion and TV recording. But at this late date, one has to be brutally realistic and honest: most of them were poorly engineered garbage. The Toshiba XS series was the textbook example of this. On paper, they're amazing units: the best recording quality and most extensive feature set (by far) of any consumer video decks ever sold. Unfortunately, Toshiba stuck them with unbelievably defective burners and hard drives.
Nonetheless, the XS series was very popular with videophiles because the PQ was superb (whenever they actually worked). So for several years, the number one topic of forums like this was "how can I replace/repair my Toshiba XS burner?" For a time, it was possible to trick some of the XS models into accepting a standard generic LG or HP dvd drive, but that time is past and those particular PC burners are long since gone. Today, once a Toshiba XS starts giving you burning errors, it needs to be discarded- repairs are no longer practical (unless you can find one of those rare old burners it will accept, and can tolerate lost functions).
About the only "cure" you can try (if you haven't already) is to buy some JVC/TY Premium Silver Lacquer 8x-speed DVD-R blanks. This is the precise Japanese blank media your Toshiba XS-35 was based on. Usually, when a recorder starts acting up, switching to these premium, "slow" blanks will get them burning again. But no guarantees: it may be too late, or the recorder will still die sooner rather than later. Also, the mfr of these blanks went out of business two years ago so "new old stock" is rapidly dwindling at web dealers. The "TY" discs are now being made by CMC Magnetics, not nearly as well as the original TY-run factories.
One way or another, you'll eventually need to migrate away from DVD recorders. Look into PC capture options for VHS, like Hauppauge USB Live 2, EZcap or I-O Data GV-USB2. Your XS-35 will still be useful as a pass-thru signal processor, connected between VCR and USB video device. For TV recording, consider iView, Homeworx, or a second-hand TiVO (all of which can offload recordings to your PC for permanent HDD storage or burning discs).
If you really cannot abide moving to a PC workflow, your only realistic option in a new DVD/HDD recorder is the current Magnavox lineup. The feature set is bare bones compared to a Toshiba XS or PC, and recording quality from VHS is not as good. But being current designs, the Magnavox burners will function reliably with any blank media. They are far less picky about blanks than any "premium" older Toshiba, Panasonic or Pioneer you could buy second hand. Personally, I would go the PC route: the Magnavox is pricey for what it is, and not all that great compared to the classic recorder you're used to.